It's true that since 2007 charges have been
laid by the police in a few cases, these have been challenged, and variously overturned or thrown out from court.
So, enforcement was certainly attempted and people were certainly detained for periods of time and forced to defend against charges that were laid.
It's not readily clear how often charges under Section 377 (1860-) or Section 377A (1938-) were laid in Singapore prior to 2007 (or of the charges laid how many cases came to trial and how many convictions occurred).
~ https://en.wikipedia.org/wiki/Section_377A_(Singapore)#Const...