As someone who got their photographic start shooting skating, I’d love to chime in on this one. I’ve definitely noticed the trend OP is describing, but if I could ramble a little…
I feel like the JOB of a skateboard photo is to tell the story of the trick. I should, assuming I have a basic understanding of skating, be able to look at a skate photo and interpret what’s happening. Think basic fisheye from the bottom of the set kind of photo: you’ve got the run up in one corner, the landing typically in the opposite corner, and the action in the middle. There’s a clear story there. In that functional sense, the timing of the flip trick only matters if it makes it harder to tell what’s happening (like when your local journalist or aspiring art student snaps a skate photo before someone has even finished popping and flicking a trick).
The magic of a REALLY good skate photo comes from nailing your timing (and lighting, but that’s a whole other topic). To some degree you can have rules for timing to consistently get something decent, like waiting till a skater drops their arms back to their sides after they pop, but they won’t always work. I don’t think there’s one right way to do it, but as the photographer you should definitely try to be intentional about it, since it’s going to make a difference in the feel of the photograph.
I think the “messier” kind of shots we’re talking about where the board is much more mid-flip, are at least a little bit a response to how much innovation was going on at the time. New tricks and technical innovation demand photos that demonstrate how new and innovative those tricks are. The way the board is flipping is important visual information to some 10 year old who has only seen photos or maybe watched a few skate videos at their buddy’s house.
Fast forward 30 years and countless videos later, we can all fill in the blanks on a kickflip, 360 flip, etc, since we’ve seen them on video hundreds if not thousands of times, probably in slow motion at 4k60 at this point. The mystery isn’t there to the same degree, so it might be that the photographer isn’t as tempted to focus on it. I’d argue you don’t see sequences as often these days for a similar reason.
A flip trick, shot just as it is reaching its peak, just before or at the beginning of the catch, might be a more subtle way of telling us how the board is flipping, and gives the photographer a chance to focus on showing pop, distance, speed, and style in a different way. If we understand it’s a 360 flip any way, showing us a different kind of timing is a nice way to fill in more info and experiment.
Neither is inherently better or worse, they just direct the viewer’s attention differently and can be more, or less, successful depending on what/who you want to capture.
TLDR: both are cool. If you’re the photographer, think about what’s cool about the trick/skater you’re shooting and how your timing can help show that off.