Early in the process yes, but not before F, by which point you already have a line forming at the airplane door/galley, so the extra 20 seconds with the GA reduces your time waiting for F to get organized.

The real issue may be added time if GA has to reassign seats - not sure what was "wrong" with the old process of FA's doing their job and worst case scenario asking a few people swap seats. Anybody know what motivated this change from UA's perspective?