No, you get Firefox.
There is much more to a web browser than just its rendering engine. When you install Firefox on iOS, you get Firefox. It uses the WebKit rendering engine, but it’s still the Firefox browser.
To be frank, it’s pretty insulting and dismissive to all the people putting huge amounts of work into building browsers only to for you go around telling people that all their work is really just a mirage.
You are a responding to a comment asking what browser engine you get, and the answer is Safari/Webkit.
It absolutely is a mirage. It's like those Ferrari kit cars where you take a Ford or whatever car frame and remove the outer shell and put a Ferrari shell on top of it. It's not a Ferrari, it only looks like a Ferrari.
The browser engine is the majority part of the browser, everything else around it is window dressing. So when you install Firefox on iOS, you are getting Safari with a thin wrapper around it. You are not getting the Firefox rendering engine, which is the most important part of a web browser.
You may wish to re-read the comment you respond to. To quote:
> Which browser engine are you getting on iOS when you install Firefox?
Emphasis mine.