This didn't get a update since june and I also hit the same issue on the aqara switch. The original post makes it clear.
Some detail in case it helps. Device: Aqara Light Switch H2 EU (firmware 1.0.1.0, 4 buttons / 2 relays, Thread), on a C-8 Pro running current beta, with a custom driver.
matter.eventPath() already returns an isUrgent field, and it goes through to the subscribe command:
he subscribe 0x00 0x02 [... {"ep":"0x05","cluster":"0x003B","evt":"0x0001","isUrgent":"false"} ...]
If I set that field to true in the map, with both "true" and Boolean true tried, the command carries "isUrgent":true, but the subscription never comes up: no priming report after 30 s. The same paths with "isUrgent":"false" are confirmed in under a second.
With non-urgent events, the switch holds InitialPress on the two wireless buttons until something else triggers a report. Comparing event timestamps against arrival, I’ve seen delays of up to 9.5 s. A shorter max interval doesn’t help, because the device appears to pick its own. HA’s Matter server subscribes to the same events as urgent and gets them instantly.
So it looks like most of the plumbing is already there. It would be great if isUrgent: true could be passed through.