This is not a regression. Tested in //UE5/Release-5.2 CL26001984
After assigning an IES Profile to a light the icon for that profile updates to a gradient bloom preventing the profile from being preview by the icon.
The icon for the IES Profiles remains the same allowing the user to preview the result of the profile.
The Icon updates to a gradient bloom.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-195365 in the post.