Nah, I fixed it for 2.55/2.60, and I will apply the same fix in 2.53. I knew what it was as soon as @ywkls reported it on Skype, but I wanted him to post it here as a reminder for me.
For the record, this affected CollDetection for lweapon, eweapon, and npc; but none of the other vars, or functions seem to have an incorrect return type at this time. My apologies if this created extra work for you @Saffith . I merely needed a reminder, and I asked @ywkls to post it in the dev chat. I didn't expect him to submit a full bug report, although it was nice of him to do that.
Update: Fixed for 2.53/2.50.2.1.sheep, too.
P.S. @ywkls : if ( ptr->CollDetection ) only worked because float is typecast to bool in that type of statement. When there is an explicit COMPARE to a boolean type (true/false), the proper bool return is mandatory. -- Clearly, no-one had ever tried if ( ptr->CollDetection = true ) in the past ???.