I found this article very difficult to follow (partially, I suspect, because of non sex based pronouns) but yes, it does seem that this man is in a women's prison despite retaining his penis.
"Fifty-one [transgender prisoners] (17%) were in female prisons. The majority of these (48) self-identified as transgender male, the remainder self-identified as transgender female, non-binary, in a different way[footnote 13] , or did not provide a response."
This is from the HMPPS Offender Equalities Report 2023/24
Published 28 November 2024. So this does suggest that there are up to 3 trans identifying males in female prisons. Note that these numbers don't include prisoners with a GRC of which there are 10.