Page opened on Firefox Android causes enormous data usage. What could cause this?

I have opened the rather innocuous page on reputable website Quanta Magazine:

https://www.quantamagazine.org/cloud-loss-could-add-8-degrees-to-global-warming-20190225/

using Firefox Android 65.0.1 (with NoScript installed) and left it open.

The data usage rapidly burned through 1 GB of data transfer via the mobile network, which is more than I use in a month in general.

I closed the page, stopping data usage. Reopened it and on it went. It has blown my data usage for the month out of the water.

I have pumped the URL through

https://sitecheck.sucuri.net/

just to make sure whether there is known evil in that page but it comes up blank.

What could be going on, and do I find out?

Enormous green disk

When I open a Google Docs document anonymously from my desktop computer (Windows 7 + Firefox esr 52), I always get this enormous green disk at the bottom right:

Big green disk Clicking on it has no effect, except for the smaller white “Explore” button inside. Clicking on that white “Explorer” button opens the pivot table tool.

How can I get rid of that disk so that it won’t reappear in the future when I browse Google Docs anonymously?

I guess it has something to do with the “Explorer” feature, but whoever thought it would be a good idea to make it take a sixth of my total screen space must have been high at the time.

[Edits]:

By “anonymously”, I mean “not logged into my Google account”, not “using the Private Browsing feature of Firefox”.

RubĂ©n’s answer implies that it could be done by upgrading Firefox. So I should add that I don’t want to upgrade Firefox. Maybe something about cookies keeping my preferences while browsing Google Docs without being logged in Google?