Checking

lkocman@rcm-dev:qgnomeplatform> locate-rhel7-rpms qgnomeplatform | grep -v debuginfo
Searching in /mnt/redhat/nightly/latest-RHEL-7/
Client/x86_64/os/Packages/qgnomeplatform-0.3-3.el7.i686.rpm
Client/source/tree/Packages/qgnomeplatform-0.3-3.el7.src.rpm
Client/x86_64/os/Packages/qgnomeplatform-0.3-3.el7.x86_64.rpm
Server/ppc64/os/Packages/qgnomeplatform-0.3-3.el7.ppc.rpm
Server/ppc64/os/Packages/qgnomeplatform-0.3-3.el7.ppc64.rpm
Server/source/tree/Packages/qgnomeplatform-0.3-3.el7.src.rpm
Server/ppc64le/os/Packages/qgnomeplatform-0.3-3.el7.ppc64le.rpm
Server/source/tree/Packages/qgnomeplatform-0.3-3.el7.src.rpm
Server/s390x/os/Packages/qgnomeplatform-0.3-3.el7.s390.rpm
Server/s390x/os/Packages/qgnomeplatform-0.3-3.el7.s390x.rpm
Server/source/tree/Packages/qgnomeplatform-0.3-3.el7.src.rpm
Server/x86_64/os/Packages/qgnomeplatform-0.3-3.el7.i686.rpm
Server/source/tree/Packages/qgnomeplatform-0.3-3.el7.src.rpm
Server/x86_64/os/Packages/qgnomeplatform-0.3-3.el7.x86_64.rpm
Workstation/x86_64/os/Packages/qgnomeplatform-0.3-3.el7.i686.rpm
Workstation/source/tree/Packages/qgnomeplatform-0.3-3.el7.src.rpm
Workstation/x86_64/os/Packages/qgnomeplatform-0.3-3.el7.x86_64.rpm
Searching in /mnt/redhat/nightly/latest-Supp-7-RHEL-7/

Seems like qgnomeplatform is on main variants (except of ComputeNode) all arches

lkocman@rcm-dev:qgnomeplatform> locate-rhel7-rpms  highcontrast-qt  | grep -v optional | grep -v src | grep -v debuginfo
Searching in /mnt/redhat/nightly/latest-RHEL-7/
Client/x86_64/os/Packages/highcontrast-qt5-0.1-2.el7.i686.rpm
Client/x86_64/os/Packages/highcontrast-qt5-0.1-2.el7.x86_64.rpm
Server/ppc64/os/Packages/highcontrast-qt5-0.1-2.el7.ppc.rpm
Server/ppc64/os/Packages/highcontrast-qt5-0.1-2.el7.ppc64.rpm
Server/ppc64le/os/Packages/highcontrast-qt5-0.1-2.el7.ppc64le.rpm
Server/s390x/os/Packages/highcontrast-qt5-0.1-2.el7.s390.rpm
Server/s390x/os/Packages/highcontrast-qt5-0.1-2.el7.s390x.rpm
Server/x86_64/os/Packages/highcontrast-qt5-0.1-2.el7.i686.rpm
Server/x86_64/os/Packages/highcontrast-qt5-0.1-2.el7.x86_64.rpm
Workstation/x86_64/os/Packages/highcontrast-qt5-0.1-2.el7.i686.rpm
Workstation/x86_64/os/Packages/highcontrast-qt5-0.1-2.el7.x86_64.rpm
Searching in /mnt/redhat/nightly/latest-Supp-7-RHEL-7/

Requires are set in this way
Requires:       highcontrast-qt5%{?_isa}


And in this way qgnomeplatform and highcontrast-qt seem to be equal. Moving back to ON_QA

Hello Jan, as an owner of qt advisory, I expect that we're interested only in highcontrast-qt5 right? 

-qt and -qt4 subpackages ended up in optional since nothing explicitly requires them.

We are interested only in highcontrast-qt5, which should be pulled in by qgnomeplatform. For -qt4 version we don't have support in Qt4 which would use it automatically so it can be used only when specified explicitly and nobody probably does that and -qt subpackage is just a metapackage requiring both -qt4 and -qt5 subpackages.

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-2018:0700