Verified in Satellite 6.3.4 Snap 1.

I followed the reproducer steps, then deleted the host (via ui) with no issues.

delete from cp_ent_certificate where entitlement_id in (select id from  cp_entitlement where consumer_id = '8a90c4a665ce42af0165cef0b8f4258a');
delete from cp2_pool_provided_products where pool_id='8a9084f364dd03de0164dd1c949e42cb';
delete from cp2_pool_source_sub where pool_id='8a9084f364dd03de0164dd1c949e42cb';
delete from cp_pool where sourceentitlement_id='eb78149b5beb4911aa09a4a1ff6cffba';
delete from cp_entitlement where consumer_id = '8a90c4a665ce42af0165cef0b8f8675a';
delete from cp_installed_products where consumer_id='8a90c4a665ce42af0165cef0b8f4258a';
delete from cp_consumer where id = '8a90c4a665ce42af0165cef0b8f4258a';

See attached video for verification of host deletion.

Created attachment 1483085 [details]
verification video

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/RHBA-2018:2915