1 and 2 are chases. 1 forces sideline while 2 marks the dump, 2 does not follow the dump back into the endzone as that is a negative pass.
If they bring 3 handlers back 2 can pick up the new man leaving their only free pass backwards.
If they play an iso, the breakside deep can move in on the iso, cutting off the breakside. Although this leaves the other deep 2 on 1, that is a tricky throw and less likely to succeed than than the throw to the iso.