All sounds good to me. What I don't get is how running on arm64 would speed up i3. I3 is already fast enough to be unnoticeable, hardly performs any expensive operations.
I believe they're commenting on the fact that the sway Wayland compositor seems faster than i3. Might be due to how Wayland handles frame rendering, but switching between the two I tend to notice a more "snappy" effect from sway
So more likely they are comparing wayland and X.
I didn’t see OP saying ARM increased performance, just that sway felt more buttery/smooth and easier to configure.