This past spring I bought a purolator, pure one, PL14612 and it was concave, and installed it with no issues.
2005 RSTD
Yesterday I went to buy another one, first at Walmart, not the pure one though, and it was convex, then went to Farm and Fleet and the pure one also was convex, so went to an auto store and the pure one was concave, so I bought it. Got back home and went to the local auto store to get another one, and it was convex. I explained what was going on to the guy and he asked why I didn't just buy the motorcycle oil filter.
Purolator Powersports, ML 16817 is the one listed for our bikes, and it is concave, so I bought two, and it says on the box Anti-drain back valve minimizes engine dry start.
The regular purolator filters are white, pure one, yellow, and the MC are black. (for what it is worth)
Thanks for the great concave/convex pictures. They tell it all.