Yes it can - and you can actually make it get smaller without chastity. warpmymind.com has a bunch of penis shrinking hypnos that really seem to work. I did one (I think it was by EMG?) and it worked because right now, my penis when it's soft, is non-existent, and my erection dropped from 6in long to 3 and 7/8 in long. It was the weirdest thing because the first time I did it - i truly tranced out, which I had never done before. and sure as can be, it seems to work. I am trying to do it again to kind of back it up, maybe lose some erection length - but, so far I haven't had the time.
I'm also trying to work on becoming a premature ejaculator - but that ******* is an hour and 12 minutes long - I haven't had time to get into that one.