FWIW: The "re-establish" comes from the FED casebook (7.3.5 Situation E) [typos are mine]
With less than two outs, R1 on second and B2 at the plate, R1 attempts to steal third. In the process, B2, who bats right-handed, after swinging or not swinging at the pitch (a) makes no attempt to get out of the way of F2 throwing to third or (b) is unable to make an attempt to get out of the way of F2 throwing to third. As a result, F2 cannot make a play on the runner. Is B2 out, and must R1 return to second? RULING: B2 is not guilty of interference in (a) or (b). B2 is entitled to his position in the batter's box and is not subject to being penalized for interference unless he moves or re-establishes his position after F2 has received the pitch, which then prevents F2 from attempting to play on a runner. Failing to move so F2 can make a throw is not batter interference.
So you want to be an umpire - read the case book - it'll remind you why there are those in the stands that refuse to de-assify themselves from their lofty perch ;-)