I agree. High round picks get a lot of chances to fail, while low round picks have to rake a lot before they move up.
Teams have nothing to lose other than a minors roster spot (and a couple years of Minimum salary) so when you have invested a Million you can wait the whole 4-5 MILB years to see if he makes it.
BTW I don't think MLB Teams think in Terms of "that Player has to replace Player x". they just accumulate as much Talent as possible and then worry about the spots later. some fans ask themselves why a Team good in pitching/hitting and bad in the other still sometimes draft the guys they have in a Surplus but for example if a Team is more confident in their pitching developement they might continue to draft pitchers to trade them later when their stock is higher.
epstein for example continued to draft hitters after the cubs already had a super deep farm on the hitting side because the cubs did well developing hitters and he could still trade some hitters later (for example torres for chapman).