Yeah it's interesting. I wonder if it's done on purpose or if it has to do with the way bots/crawlers are counted
See parent. The default in FF is to shim the GA script
Also GA requires opt-in in the EU (even if some sites try to be clever and illegally make it harder to refuse than to accept) whereas presumably their first-party tracking is done in such a way consent is not necessary (e.g. sufficient anonymization that a data point can not be correlated with the user it originated from). Presumably FF users are more likely not to consent by default to begin with.
> this is Germany, generally far higher FF usage
But the interesting part is not how much FF has here, but how much GA undercounts it.