Fortunately we do have migration stats to work off of:
(migrations from SO over the past 90 days)
- superuser.com × 222 - 8% rejected
- dba.stackexchange.com × 158 - 9% rejected
- tex.stackexchange.com × 115 - 7% rejected
- meta.stackoverflow.com × 89 - 29% rejected
- codereview.stackexchange.com × 70 - 2% rejected
- programmers.stackexchange.com × 41 - 7% rejected
- webmasters.stackexchange.com × 36 - 5% rejected
- unix.stackexchange.com × 26
- wordpress.stackexchange.com × 24 - 4% rejected
Programmers, once upon a time, was a migration target for non-mods. Because of some unfortunate misunderstandings and radical changes surrounding the site's scope, it ended up being treated as the garbage bin for SO, in which any question SO didn't want they just migrated to programmers to deal with. Because of the influx of crap, it needed to be removed as a migration target.
While it would be somewhat interesting to know if the mods are seeing a lot of flags requesting migrations to programmers that they are rejecting (See the comments below for some anecdotal comments; thanks mods), at the end of the day with only 41 migrations in 90 days it's not a particularly large number of migrations; that seems entirely within their capabilities to handle.