You just link to a graph showing the sizes of the Firefox binary on various platforms across different versions. It has nothing to do with RAM.
Firefox definitely wins out in memory with more tabs because Chrome's process-per-tab model accumulates overhead for every process, while Firefox's tabs are more lean.
Thats alright. A single chrome tab is regularly >150MiB, and thats for plain sites!
(edit: this seems to measure the size of the installer binary. I think you wanted to link https://areweslimyet.com/ which shows Firefox using <512MiB with 30 tabs for popular websites open)