Guaranteed. I've been taught that as well -- if you don't have a clear lane to throw, throw at the runner. For example, consider the little nubber, where the pitcher is point A, the first baseman is point C and the runner is point B:

-- A
-------------------------------------- B -- C

No way he can make that throw. But instead, it was set up like this last night:

------- A


-------------------------------------- B -- C


Peacock had a clear lane to throw; I'd wager it'd be much tougher to try to throw at the runner and try for obstruction than it would be to try to make a good throw from where he was on the field.