I just tried this on a version of TVH that I compiled in the last few months and it seemed to work fine for me.
I created an AutoRec for a programme on a channel that I knew would contain a CRID (content reference identifier). This produced 5 recordings (Mon-Fri) as I expected. I then edited the AutoRec to record only Tuesday and Wednesday and the recordings for the other 3 days were deleted.
I also tried this on version 4.2 and it also worked as expected.
What version of TVH are you using?