There are other things too, like pressing `*` then using `:%s` is no different than the behaviour they describe. I use a plugin that shows you all the updates live as you type making it essentially the same as multiple cursors (for this example). The only difference is that you're typing on the command prompt as opposed to the current line.
I really liked helix, but the problem is that pretty much everything I use is setup using Vim bindings (shell, browser, ideavim,...) so switching to helix concept of editing was different enough to require effort, but close enough that it screwed up all my other muscle memory.
But ya, I'm way too invested in Vim to bother with Helix. I have years of scripts and plugins I've written. I can't even be bothered to switch to nvim (I tried once and was not fun).
The way :s works in Neovim looks like multiple cursors to me, but I’m not familiar enough with Helix to know what the difference is.