Yesterday this was my experience at FRA:

10 min. before official boarding time 0905, I asked the GA if my u/g had cleared. She said the UG list would be determined at 0920 when they'd call by name and that I had should come back and wait by the side.

At 0920 there were 4 of us waiting. Boarding had started. Nothing happened until almost everyone had boarded. Meanwhile, one passenger had rushed in from out of the blue and after some lengthy inquiries with a GA did what I think was a LMU (saw him later in J). One of us who later approached the GA counter was told J was very tight and that he should board and if anything came up they'd find him. Finally, only when no regular passengers were waiting to board did the GAs start determining the UG list and printing BPs. Mine was the second of two names to be called and we were handed our BPs - after 0940. It certainly wasn't good for the third passenger who was practically the last to board Y (full overhead bins, etc). Though I doubt it, I hope, if he didn't have one, that they reassigned him my original 'preferred' exit row Y seat instead of letting it be grabbed by someone at random.

There surely ought to be a better way. The concerns about missing out on priority boarding are valid - worse if one's going to be among the last to board. AC need to review their practice. If they have the BPs printed well ahead, fine, and if there are many seats up for grabs I don't know how practical it would be, but at least on flights where they know only a few seats are going to be involved, I think they ought to let people board and then move them up from inside (and if someone chooses to wait outside for the u/g because it's too much hassle boarding and changing seats then the trade off with priority boarding is their choice).

In contrast to ACA321's experience, at least the GAs in FRA were reasonably polite!