"Flair" is either a natural aptitude for something or a synonym for
panache.

Flare is rounding out the end of something, think flared trousers or flared
tubing. In our case it refers to the transition from a (relatively) steep
approach path to a brief period of flight parallel to the landing surface.
Whether you land on the mainwheel or both wheels together is irrelevant, &
purely a matter of choice.

One reason for landing on both wheels is that it's virtually impossible to
bounce back into the air again.

Really good point. Thank you for pointing this out to me.