Upstream patch:
https://github.com/ClusterLabs/pcs/commit/a5028f663a7bf0142a7573afab5e045fc0f4249e

After fix:
[root@rhel81-node1 ~]# rpm -q pcs
pcs-0.10.1-6.el8.x86_64

[root@rhel81-node1 ~]# pcs resource describe ocf:pacemaker:Dummy | grep unique
  state (unique): Location to store the resource state in.
  passwd (unique): Fake password field
  op_sleep (unique): Number of seconds to sleep during operations. This can be
  envfile (unique): If this is set, the environment will be dumped to this file
[root@rhel81-node1 ~]# pcs resource create R1 ocf:pacemaker:Dummy state=1 --no-default-ops
[root@rhel81-node1 ~]# pcs resource create R2 ocf:pacemaker:Dummy state=1 --no-default-ops
Error: Value '1' of option 'state' is not unique across 'ocf:pacemaker:Dummy' resources. Following resources are configured with the same value of the instance attribute: 'R1', use --force to override
[root@rhel81-node1 ~]# echo $?
1
[root@rhel81-node1 ~]# pcs resource create R2 ocf:pacemaker:Dummy state=1 --no-default-ops --force
Warning: Value '1' of option 'state' is not unique across 'ocf:pacemaker:Dummy' resources. Following resources are configured with the same value of the instance attribute: 'R1'
[root@rhel81-node1 ~]# echo $?
0
[root@rhel81-node1 ~]# pcs resource config R1 R2
 Resource: R1 (class=ocf provider=pacemaker type=Dummy)
  Attributes: state=1
  Operations: monitor interval=10s timeout=20s (R1-monitor-interval-10s)
 Resource: R2 (class=ocf provider=pacemaker type=Dummy)
  Attributes: state=1
  Operations: monitor interval=10s timeout=20s (R2-monitor-interval-10s)

BEFORE FIX:
===========

[root@virt-141 ~]# rpm -q pcs
pcs-0.10.1-4.el8_0.3.x86_64

> No keyword 'unique' within resource options description 

[root@virt-141 ~]# pcs resource describe ocf:heartbeat:IPaddr2 | grep '(unique)'
[root@virt-141 ~]# echo $?
1

> Creating two IP resources with different name and same ip address

[root@virt-141 ~]# pcs resource create app-ip ocf:heartbeat:IPaddr2 ip=10.37.165.40 cidr_netmask=22
[root@virt-141 ~]# pcs resource create db-ip ocf:heartbeat:IPaddr2 ip=10.37.165.40 cidr_netmask=22
[root@virt-141 ~]# echo $?
0
[root@virt-141 ~]# pcs resource
 Clone Set: locking-clone [locking]
     Started: [ virt-141 virt-142 virt-143 ]
 app-ip	(ocf::heartbeat:IPaddr2):	Started virt-141
 db-ip	(ocf::heartbeat:IPaddr2):	Started virt-142

> It is possible to set non-unique value across instances of same resource

AFTER FIX:
==========

[root@virt-045 ~]# rpm -q pcs
pcs-0.10.2-3.el8.x86_64

[root@virt-045 ~]# pcs resource describe ocf:heartbeat:IPaddr2 | grep '(unique)'
  ip (required) (unique): The IPv4 (dotted quad notation) or IPv6 address (colon

[root@virt-045 ~]# pcs resource create app-ip ocf:heartbeat:IPaddr2 ip=10.37.165.40 cidr_netmask=22
[root@virt-045 ~]# pcs resource create db-ip ocf:heartbeat:IPaddr2 ip=10.37.165.40 cidr_netmask=22
Error: Value '10.37.165.40' of option 'ip' is not unique across 'ocf:heartbeat:IPaddr2' resources. Following resources are configured with the same value of the instance attribute: 'app-ip', use --force to override
[root@virt-045 ~]# echo $?
1
[root@virt-045 ~]# pcs resource
 Clone Set: locking-clone [locking]
     Started: [ virt-045 virt-046 virt-049 ]
 app-ip	(ocf::heartbeat:IPaddr2):	Started virt-045

> Cannot set value which is not unique across resource instances

[root@virt-045 ~]# pcs resource create db-ip ocf:heartbeat:IPaddr2 ip=10.37.165.40 cidr_netmask=22 --force
Warning: Value '10.37.165.40' of option 'ip' is not unique across 'ocf:heartbeat:IPaddr2' resources. Following resources are configured with the same value of the instance attribute: 'app-ip'
[root@virt-045 ~]# echo $?
0
[root@virt-045 ~]# pcs resource
 Clone Set: locking-clone [locking]
     Started: [ virt-045 virt-046 virt-049 ]
 app-ip	(ocf::heartbeat:IPaddr2):	Started virt-045
 db-ip	(ocf::heartbeat:IPaddr2):	Started virt-046

> Option --force works

[root@virt-045 ~]# pcs resource delete db-ip
Attempting to stop: db-ip... Stopped
[root@virt-045 ~]# pcs resource create db-ip ocf:heartbeat:IPaddr2 ip=10.37.165.41 cidr_netmask=22
[root@virt-045 ~]# pcs resource update db-ip ip=10.37.165.40
Error: Value '10.37.165.40' of option 'ip' is not unique across 'ocf:heartbeat:IPaddr2' resources. Following resources are configured with the same value of the instance attribute: 'app-ip', use --force to override

> Trying to set value which is not unique across resource instances through update is not possible as well

[root@virt-045 ~]# pcs resource describe ocf:pacemaker:Dummy | grep '(unique)'
  state (unique): Location to store the resource state in.
  passwd (unique): Fake password field
  op_sleep (unique): Number of seconds to sleep during operations. This can be
  envfile (unique): If this is set, the environment will be dumped to this file

> The same procedure were tested with all of the unique resource options of Dummy (state, passwd, op_sleep, envfile)

Marking as VERIFIED in pcs-0.10.2-3.el8

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHEA-2019:3311