The membership capability is still documented, with JOIN and PART. Does this mean that joins/parts from other users in the channel are still going to be sent by the server, just not the initial full userlist? Otherwise I’m not sure what the point of the membership capability is, since of course a JOIN/PART for yourself when joining/leaving a channel is sent by the server either way.
(Also, the “Join a channel” section still mentions the removed capabilities.)