Selected Objects Turn Pink in Lightmap Density View Mode.
Works as expected in 4.21 CL# 4753647
Found in 4.22 CL# 6063286 and 4.23 CL# 6395561
This is a regression.
It will turn pink
The outline would appear to show its selected but I can still see the lightmap information
There's no existing public thread on this issue, so head over to AnswerHub just mention UE-74799 in the post.