The people getting rides to the border were technically "illegal" (propaganda term, there's nothing wrong moving around) already as Russia was skipping the visas etc.
I'm not even that sure on how much this is geopolitical action or just corruption at play.
If whoever benefits (at least money) from transferring people towards a border out of there it might continue, even if the people might have to try around a closed border crossing.
The way that the traffickers and Russian authorities sold the idea to the migrants was that you'd get in nice and easy and that Finland was the door to the EU.
Harder to sell those trips if the border is closed, guarded and those trying to cross are yeeted back. Why pay to get here if the outlook not so good and there's opportunities to get in closer to your starting location.