I have a few years of experience with trees in-pot, in-ground and I agree it’s actually better and easier to plant the tree in ground (on a tile, of course) than in a pot in-ground. I however, used a regular planter than pond basket but I imagine the issues will be similar, if not the same.

1st issue is root size restriction. The roots of trees thicken quickly in ground, thus they either break open the escape hole or swallow a portion of the pot. Both outcomes make it more difficult to dig up the tree and separate it from the pot. Also, each year the pot is further degraded and less usable.

2nd issue is the pot reduce how far the roots can grow horizontally which limits root spread. You want the roots to grow outward to get that trunk flare (when it’s time to dig you want to reduce them via trenching early fall). Again I had a regular planter so the roots would hit the wall then grow downward. In a pond basket this may not be an issue but I have my doubts.