There is a difference in implementation and set of checks that are made in GetKnownPerceivedActors() depending on if you use specific SenseClass or leave it as nullptr (so it will return info for all available senses).
This was reported and tested in 4.21.2 (CL-4753647). This was reproduced in 4.20.3 (CL-4369336), 4.22 (CL-5365847), and Main 4.23 (CL-5423312)
Results: GetKnownPerceivedActors used with Sense class is returning senses that is already forgot.
Expected: GetKnownPerceivedActors used with Sense class will return nothing once the senses are forgotten.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-71678 in the post.