According to the latest post:
We had an omission from our most recent patch notes. We’ve changed when the roster lock occurs for both TW and GAC matchmaking. Previously, your roster did not have a snapshot of your collection taken until the moment matchmaking had begun. This resulted in some players rosters being updated after the moment matchmaking by the nature of the system going through and taking snapshots of everyone’s roster. Now, when you click the Join button your roster is snapped. For TW, if you exit, you are removed from matchmaking consideration. When you rejoin, your roster is snapped again at that moment. Apologies for the omission.
When does the actual "lock" happen. This post could be taken one of two ways, either...
1. Your roster is recorded when you join and that's when the lock happens.
2. Your roster status is recorded when you join and locked at the time or matchmaking. When it it locked the update happens much faster because 90%+ of the data is already recorded and it simply needs to be verified.
Option 2 cuts down on the write time and input/output time for the roster lock and would definitely speed things up, but I'm not sure what the post is specifically saying here.
Can you please clarify?
If the answer is option 1, can you clarify as to why? If I am upgrading toons and having to join/leave an event it increases the chance of guild members missing the event altogether by being focused elsewhere or simply waiting too long and life happens.