You could, but few are in the perfect storm of opportunity he is - a QB that's currently maligned but might just be a whole lot better this year than last and no real competition for targets in the most wide-open WR corp in the league. And while his physical profile took a bit of a hit after his pro-day it's still more impressive than most UDFA. If Keelan Doss goes out and does those kinds of things the response will likely be "meh, AB is there, his ceiling is capped" or if Stanley Morgan does it'll be "well, he's pretty ordinary, and it's Dalton, and there's AJG and Boyd there". Preston Williams has none of those things in front of him aside from mistrust of Rosen's future. Personally I think Rosen got hosed in ARI and still has a better than average chance to turn out to be a very good QB and he doesn't scare me one bit. So if HE goes out and looks good, bringing Preston Williams along with him, that's got a chance to skyrocket both their values. That's what I'm looking at.
In a 12 man he's a lot harder to roster, I do get that, and I did specify I held him only in 16 man leagues. He was actually drafted in my 12 man leagues, and way early for my taste.