If there's a base, it makes sense that it's a kanto one. They're saying that the anime is not galar only. The kanto base can be used for gen 8, 9, 10 or whatever needed. A galarian one wouldn't have the same effect.
So Ash comes back to Kanto, talks to a new professor, meet 2 new friends with galar pokemon there and moved by the curiosity about this new pokemon and friends all of them go to galar. Could it be the start?
I see no problem in this.
Look like when "alola kanto" came with mega evolutions for brock and misty.
The "new regions" and their new pokemon always existed somehow. They just haven't appeared yet. I mean - it was always possible for a yamper to live in kanto, we haven't just seen it yet.