Here to burst some bubbles. But it was not called a mountain in the chapter and
is massively smaller than one. We see it right in front of AFO and it's close, it's clearly smaller than Machia. AFO is hard to use as a scale due to him being younger and likely smaller as well. Wouldn't change the results by much I imagine, but that feat isn't good enough.
Well I admit maybe it could be good when we get the clear scans. Since there is something I need to see in better detailed. But don't hold out hope for too much. Also maybe next chapter will show a different angle, since I'm certain we'll get a flashback.
The distance Machia would have to travel would've been around 70+ km going by my quick measurements with google. Which would take him 40+ minutes to travel. Since he can't burrow underground with people on his back.