Unfortunately, in general, people tend to just read, vote, and then forget about it without checking back: that's why I always try to add some source or ways to verify what I post.
And - in this specific case - probably some people just like LTT, I assume.

Probably when you installed the second linux you overwrote the boot loader instead of adding a new UEFI entry point.
But I've never had a Mac, so take this with a pinch of salt, and honestly considering things can change based on what, in which order, and how you installed things.. it could be something else.