I know what a bypass valve or ADBV looks like, and I think Mr Hayes does too. However - he can clarify given your description. Some claim that the ADBV keeps oil from draining out when the filter is mounted (more or less) sideways; I've heard that it can leak out overnight. Backflow crudding up the oil pump sounded like the best reason to use an ADBV. I'd guess that oil flow would be marginally better without an ADBV.
As for the bypass valve - some cars don't have it in the filter. An ACDelco PF47 (or equivalent) for my dad's '96 Buick Regal has none. I think the car has a built-in bypass somewhere near the filter mount. This was the same for another the AC PF52 filter I used on a Chevy Lumina APV minivan. There was a previous version (AC PF51) that was identical except for no ADBV. Both the Buick and the Chevy had the base pointing up, so gravity keeps oil in the filter.
As for bypass valve designs - I've seen a whole slew of different kinds:
1) Cheesy Fram design with a piece of plastic and a spring. 2) Metal/rubber with spring at the end. 3) Metal/rubber bypass surrounding the outlet (Wix)A newer Champion Labs design has 6 holes at the far metal endcap, with a large piece of metal covering the holes on the other side. I'm not sure what's at the other end, but I would assume some sort of spring and/or a gasket.