This entire situation is so unnecessary. Maybe it was about budget. They didn't want to bring in two more guest stars for Caleb and Spencer (significant others) so they thought let's throw Spencer and Caleb together and save some money.
Seriously, probably not but nothing about this storyline makes sense. It's one thing to break up Hanna/Caleb (even if MK should have stopped while she was ahead, she created a sound, healthy pairing, so let them be stable and survive the time jump) but quite another to throw Caleb in between Hanna and Spencer. Dumb.