Tested on 1.20.15, issue appears to persist with a dedicated server and client.
Just did some further testing on 1.20.12, and I noticed that the issue persists under normal configuration, but was unable to reproduce when the Experimental crawling feature was enabled on a local copy of the affected world.
Based on my tests, this issue may be limited to portals created in the cherry grove biome, as portals elsewhere seem to function normally.
The world in which I originally observed this behaviour is a vanilla multiplayer server, in Survival. I've been able to reproduce it on a local copy of the world, as well as a different world that used the same seed, was created locally, and has only been played locally.
I also tried a new world with a similar spawn (ie. in a cherry grove biome), and did initially observe some suffocation damage, but was unable to reproduce the original issue in the different world.
The seed for the impacted world is 842595. The other seed I tried was 447.
Thanks for the assist! Apologies for not adding to the main ticket; I had done some searches, but I'm also familiar with the limitations of Jira's search.
Ok
why did i put it as java
Tested on 1.20.30, issue persists.