This issue is caused by the following lorax bug:
Bug #1826479 - Lorax copies wrong OS artwork into anaconda
It is dependent on that bug getting fixed. There is a workaround posted you may be able to try?
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-2020:2572
Created attachment 1680203 [details] RHGS 3.5 RHEL 7 ISO screenshot (correct logo)