I'm in DM33 and have had similar passes on the last one for the night. Typically, in a S to N pass, activity picks up late in the pass but not always. There have been passed where I've talked to another Phoenix station for 2 min. and no one else chimed in.
I always thought it was due to being near XE land and not many stations being on from there but it just might be that it's late. In a town the size of Phoenix and the rest of the valley, I only have heard 15 or so unique calls on FM and several are snowbirds so they are preparing to head north. Having said that, LA is huge and they almost always have a few on every pass.
I did have one time where a linear bird was up as well and that split the regulars up.
I'm any case, if you can get full duplex operational, you can be sure you're getting in.