As JAL offers premium airport services only to F and status customers (the domestic “class J” has a better seat but no airport benefits), the airport services on non-F routes are based solely on status.

In the larger airports, F and OWE check-in is a completely separate area with a dedicated security check that exits directly to the lounge area. Also, the larger domestic airports often have separate OWS and OWE/F lounges, although even the latter can be crowded at times. I often travel with a checked bag on longer trips, and sometimes there can even be a line at the OWS check-in. Priority security is also often OWE/F-only, although I have seen the odd OWS line at Naha. Thus, you never have the lines you can se in HEL priority security where even OWR is accepted.

Also, JAL has a two-tiered priority baggage sysyem, with OWE/F pax getting the higher tier. This has been very consistently enforced on all domestic flights. Finally, the front seats in Class J are blocked for OWE only (even on full-fare flexible tickets) making it easier to find good seating (Class J is often quite full in my experience, people seem to value the better seat).

Calling this a lifesaver was perhaps a slight exaggeration, but on the other hand many train connections have been saved by the rapid bag delivery. Individually, these details are small, but taken together it makes me value the OWE status. So for now, JAL is motivating me to keep AY plat (which does not require me to go too much out of my way).

Edit: this is of course airport dependent, as the full OWE services are only available at larger hubs (HND, ITM, FUK, OKA, CTS at least). However, still much more than AY offers at HEL for OWE on Schengen routes (the bag priority is technically there but enforcement is very inconsistent and airport-dependent).