When the windscreen fills with the enlarging image of an oncoming aircraft you correct! Who is to say that TCAS is working correctly etc etc. We don't know what they SEY crew saw but watching the RADAR plot is looks close enough to me. Yes, in Europe or other very busy airspace you might not react in the same manner but this was not Europe. The SEY crew obviously felt the situation warranted maneuvering.
To say we never react to a TA is ridiculous. We do not 'usually' maneuver based on it for all the reasons mentioned. The SEY crew saw a problem and, with perhaps the local knowledge that the airspace is not busy (hence no chance of multiple cascading RA's) and the local knowledge that ATC is not the best, reacted.
Much better than a midair and, later on as a ghost, trying to tell the world that SOP's or some other rule forbid you from reacting.