It definitely can be done. I normally send out calls to D1s within 70 miles and up to about 510 overall. I've never noticed the 20-mile rule, but it's possible that's true. I think most of mine have been 10 miles away.
Location is a big factor, though. e.g. my Johnson & Wales team in RI always has D1 options because of the local D1 population..even signed two D1s in a 2-man class once. If you're in a more remote location, D1 pulldowns will probably be extremely rare.
fwiw where the normal D2 takes about 10 SVs to pull down, my experience has been about 15-20 for D1s.