Pardon the newbie-ness.

I've been flying frequently for a while now and started using ExpertFlyer about a month ago. I thought I had figured out how it all worked regarding fare buckets, etc. My understanding had been that fare buckets for a given flight number were independent of routing -- that the number of seats in a given fare bucket were bookable regardless of routing, actual fare, etc.

Am I wrong?

I'm looking at LGA-HNL through DFW on June 19; I want to book in V so it I get a full 1 EQP, as this is part of a platinum challenge (in conjunction with a later HNL-SYD-LAX itenerary). When I search ExpertFlyer for just the DFW-HNL leg, I get AA 5 with V7 and AA 123 with V0. However, when I search ExpertFlyer for LGA-HNL via DFW, I get varying degrees of V availability on AA 5 and AA 123 depending on which LGA-DFW flight (AA 705, 707, 701) -- that is, the number of available V seats on AA 5/123 (according to EF) depends on which connecting flight I take (they vary from V3 to V7 on 5 and V0 to V6 on 123)

Is my understanding of fare buckets, routing, etc. all wrong? Somebody please set me straight. If bucket availability depends on routing, my life might just have gotten significantly more complicated.

Thanks!