As has been stated, d3's in the Northeast truly do recruit into the spring of recruits senior year. That goes for the best programs as well. They have no roster limits and often have jv teams, so they can take a flyer on a kid who can get accepted to the school. But the bulk is finished by December after that it's more the taking a flyer route, more reminiscent of an invited walk-on.
That being said, I still see kids who over think their talents, all you have to do is find their twitter posts from a few years back, all saying they are going D3, because they will play "right away" and you see their stats and they haven't or have barely seen the field the past two years. Based on their posts, I guess they thought they were D1 but went where they would play, or kids still have a stigma about D3 and seem to need to give a reason they're "only going" D3. D3 is a numbers game and if you don't work your tail off to see the field, they'll just pull someone else off their jv roster who shows better.
I have seen some d1 transfers to several of my son's D3 conference schools. Not tons, but it is happening as kids move closer to home and want to see the field.