Well, the fungus fruited, the tree survived till winter dormancy (waiting for snow now). Moss is super stable in these pots, even ones where everything else died still are emerald mossy. I often find squatter birch saplings in these as well, although few make it to first year. I would count this as stable, let's see who grows there next year!

Yeah, was surprised as well, but it looks correct and they grow locally a lot. I've seen fruiting body growing smaller than normal in my constrained growing experiments (but also larger than normal sometimes).