IIRC it's always been like this with Sonar and is not a bug, but I think it flows from the structure of clips vs. tracks.
The clip length defines the totality of the clip. Therefore, clip length takes precedence over something that's a
subset of the clip, which is the case with a clip effect.
However with a track, the clip is a subset of the track. Therefore, an effect applied to the track takes precedence over the length of a clip, and the effect tail will continue after the clip has ended.
I prefer this protocol because when adding clip effects, I'm interested solely in having something happen to that clip. If I do want an effect to have a "tail," then I can slip-edit to make the clip longer but I would not want this to be the default.