JRutledge wrote... the opponents cannot block the position of the defenders close to the thrower.
Citation please, especially in the case of a single offensive player standing in that closest to the thrower spot, or in the case of a stack of offensive players standing perpendicular to the boundary line, with an offensive player standing in that closest to the thrower spot.
No way that this is illegal. We can't tell the offensive player standing in that closest to the thrower spot to get out of that spot in either of situations described above.
Parallel stack within three feet of the boundary? Sure, but not in the two situations described above.
JRutledge wrote... the defense of the throw-in has the right to stand next to the thrower as well. That rule kind of addresses that as well. It is the only time they have a right a specific space on the floor if they did not get there first.