Indeed it is, but it hurts those larger programs far less losing highly ranked recruits than it does when HBCU's get picked clean of the talent they actually are getting to commit, then leaving after a year or two.
Losing one or two 3- or 4-star recruits out of 10 in the previous year's recruiting class won't sink Alabama, LSU, or Ohio State, but for these HBCU's losing 3-4 of them when they only had 5 or 6 to begin with will certainly be felt.
Will every draft worthy player transfer from a HBCU to a larger program? Of course not, but it seems as though the majority of them will, especially now that the money is talking (always has though really). NFL scouts don't have to look too hard because the scouts of those P5 schools are already doing the work for them.