I want to disable this just for one Post Type, as it doesn't really matters if there's another user editing it (the main content editing area is Ajaxified and non-admins can only see that).
I looked at the core functions but couldn't find an entry point. From the function
wp_set_post_lock I'm guessing that I'd have to intercept the
get_post_meta, but is there an official way to do it?
And there's a second lock that doesn't seem to be affected by the filter
wp_check_post_lock_window (as shown by birgire, here in an Answer). I've tried
remove_filter( 'heartbeat_received', 'wp_refresh_post_lock', 10, 3 ); at various points but it keeps beating without respecting