I think it was more of an artistic choice that it would’ve been weird for the entire Series Finale to culminate in Ted leaving to go back to America only to show him right back in England 20 seconds later in another scene.

Like, yes, we know time will have passed, he can always come back when he feels like it, but I do feel like if they showed him right back in the UK it would’ve undercut some of the gravitas of him leaving.

Beards weeding takes place in the dream Ted is having while on the flight back to Kansas. That’s why seemingly everyone from the whole series is there and the entire scene is a bit overexposed.

Only reason I know this is because Brendan Hunt talked about it in his AMA after the final episode aired. Cheers my friend!