Locking something requires that the lock gets released and sometimes that will not be done in the normal way, because an edit is not finished in a reasonable time. Given that people might go out for a coffee (and stop typing, which might be detectable) or that a connection might go down (but the editor could come back and continue). That means you have to have something like a timeout period that needs to be determined and implemented, but the question is of course what is a reasonable amount of time.
The site doesn't implement locking, but once you have enough points to be able to edit without the need of review, you can commit changes, even if someone else got in before you, assuming that you have more substantial edits (not sure how the system determines what is more substantial).
I know, as I have done a few edits, that it can take some time to edit a post, especially if someone who posted had no idea of how formatting works on this site, but a few minutes is IMHO quite a lot time.