What's relevant is whether "/usr/bin/env bash" runs the correct one.

I used "brew install bash && brew info bash" to get the path, then ran that shell (zsh doesn't work), then inside that new bash, ran the screensaver app.

I found the 4k fullscreen perf in iTerm2 to be not-great, so I did it again in the kitty (GPU powered) terminal macos app, and it was good.