You should ask about this on the
OBRA site. You'll find people there who can tell you more about the local gravel races. I haven't done a gravel race, but from the reports I've heard it sounds like the pack gets spread out the way you describe. I definitely wouldn't compare it to a cross race though. No barriers, no grass and too long for full gas intensity.
The thing is, gravel grinding is a pretty broad term and gravel racing is just a small corner of the gravel grinding scene. You just missed (or maybe didn't miss, for all I know)
a great gravel ride in the Salem area. That was just a bunch of people going out and riding gravel roads together. A bunch of people rode it fast. A bunch rode it slow. All had fun. There's another ride like that next month, the
Dalles Mountain 60. It's two weeks before the
Gorge Roubaix, which has both racing and non-racing option, so you can get your feet wet before diving in.
Of course, the other thing you can do is just go out exploring. There are a lot of gravel roads out near the Gorge. Closer to Portland everything gets paved
but you can find some good gravel roads not too far away.