After a few more hours... I watched someone else, and in their playthrough (in an earlier game update), the 'Wall Jump' screen had a guy auto wall-jump spectacularly, whereas in my game he just bounces off the wall and runs off without jumping. I only just figured out that I can wall jump with the dash boots, though I'm still unclear what button presses/timing trigger it. Seems maybe some tutorialization is maybe broken/lacking now.
The way I'd say to do it is to jump, then dash, then mash the jump button. I will say, the timing is pretty lenient after the initial jump; you just have to mash the jump button, not necessarily time it perfectly. The one NPC in particular who tells you how to do it is in the Wall Jump room. It shouldn't be any harder now than it was in previous updates, you just can't do it in 1x1 gaps anymore. I'll check the tutorial room though; I think I have an idea of what's causing that.
Cool, he does his jumping again :)
And I realized the tutorial NPC, I only read his first batch of dialogue, talking a second time had the good stuff, which I had missed.
Somehow I am still 6.4 hours into the game with zero souls recovered, but I have found a lot of collectables and checkpoints and secrets and whatnot... is fun to explore but I still feel like I'm missing some early linchpin that is maybe supposed to be obvious - there are so many things I could do if I could hold two items :)