These two are canon, right?
Might be. Let's see it in S2
Unfortunately for our MC.
Only in the PVs.
It's an act, meant to draw in yuri shippers.
And it's doing its job, apparently
It's an in-universe joke. It was first mentioned in the 2nd PV and then dropped for the next 3 PVs. Not until the project gain popularity with MakixNico shipping that they added another one in the anime episode 9.