It doesn't work.
There is no snap in my video.
Try with this project :
https://stash.reaper.fm/v/35901/bug2.rpp
In Midi Actions, if I set "Set length for next insert note : grid" set to ON, the reduce length issue disapears...
If "Options: Drawing or selecting a note sets the new note legnth" is set to ON, the issue appears when the lenght of created note is less large than the grid...
Very strange.