All I can tell you is that the processes and memory used reported by task manager matches what the about:processes
(SHIFT+ESC) in Firefox reports. The number of processes is accurate, it just means every /thing/ FF does spawns a process, regardless of how many actual tabs are open. In both cases things were accurate and working normally, just having that gallery opened used extra RAM for whatever reason initially.
I open that gallery basically daily and have done for some time as it's a curated gallery. So it could well be Windows memory management seeing this behaviour trend and seeing that a large memory intensive task is being done by the user, and then using/pre-allocating more memory for that I guess, since Windows does do this, moreso the more RAM you actually have. None of this is a complaint, just an observation being talked about. Everything runs fast and there's no /real/ issue.
Now that I am on a fresh new profile, that memory use I was seeing before is greatly reduced, because it's effectively a new app install and Windows is re-learning usage behaviour for itt. I suspect if this is the case then the RAM use will go back to what it was before in a space of time as I continue to update the IMGUR gallery daily.