From a human perspective, it might make some sense if they are not sure if the sac is a 100% win. Stall and look for something better...The point is that by not playing the immediate sacrifice (and doing some other useful move instead) you may bring a win nearer which may ultimately not involve any sacrifice at all.
An engine on the other hand, is going to see to depth X, and all else being equal there is no reason to guess that it will be able to find a shorter or "better" win later as available time is an ever decreasing commodity. Of course if it can see the "better" win it will take it, but it won't speculatively gamble on the existence of one. The engine also does not suffer from doubt as humans do. So I would say if a human could have the certainty of an engine, he or she would play in the same way. Obviously, this is not the case, but I would say both approaches are logical given their respective operating conditions.