He made a general statement about Oregon chain, based on .325 semi chisel alone. That was what I commented on!
Anyway, the small ramps on the drivers doesn't really count as bumpers, as long as they are a substitute for much larger and ramped rakers on most chain that doesn't have them. it just is a neater way to do it. Now I haven't studied the BPX in detail, as I rarely use semi chisel, but the LPX has really small rakers and are "yellow" chain.
LPX simply is the most efficient .325 chain currently made
Over simplifying things may be tempting, but it doesn't always give you the right answers!