I'm at the side that Ash could retire, I said this long time ago. We have all the hints like tying plot points and such.
But well, more and more when I thought and still think about this specific title, I had this realization. The episode is not even about Ash. I think its a project mew episode.
The thing is, if you all remember Goh's first apperance, he didn't choose Mew, but met Mew. I think this is a callback to that specific moment of Goh meeting Mew again in Faraway Island. Since the title implies "Glad, I met you" means its a callback of Goh's first encounter to Mew, which gave Goh a life purpose.
Funnily enough, JN133 preview showed that Pokeballs don't work, so catching Mew besides befriending it, is not an option. It can be a case like Suicune.
Sure I could be wrong, but the TV guides didn't mark this episode as the final episode, so tbh what I'm saying could make sense.