Besides z being much faster (looking through a sorted list of directories visited instead of recursively walking from the current directory) your snippet looks from the cwd
Yep, that's fair. I use fzf along with z. I use z usually to switch projects (and I work in Go, so many are in GOPATH and annoying to CD to manually) but I use fzf both inside and outside of vim to open individual files.
Even in the worst cases, at least with my i7 NUC and using fd instead of find, it's less than 500ms to load the entire list into fzf.