Although then the "Wild isn't it" statement really isn't wild at all - Android is by far and away the most popular OS, not far off double Windows. Of course if you lump that in with Linux, Linux would be more popular than Firefox.
You've chosen to compare Firefox's share from all platforms to Linux's share only on desktop. I don't know whether this was deliberate misinformation-pushing, or an innocent brainfart/inability to parse data, but that's not how data is compared.
Firefox has 50-70% more users than Linux, depending on the platform you use for comparison.
No matter how you cut it, Firefox is more popular. It's more popular across all platforms as a whole, and it's also more popular on desktop.
And 4.45% of a far smaller number is not greater than 2.74% of a much much larger number.
Browsers are mostly identified by user-agent, or not? If so it isn't surprising because people like to fake that. In the least to shut down such silly messages like "please use chrome/edge"
OS is also identified by user agent, so it's no less vulnerable to fake agents. In any case, I'd wager the vast majority of users even on Linux use unaltered agents, though this isn't something that can be backed up one way or another because there are no numbers for fake agents.
I don't think that's what 'market share' is trying to represent, but without any context - yeah. You can lump in android phones and set-top boxes and signage and industrial controllers while you're at it.
From a very quick glance at Statcounter, I can only see India where OP's statement is true, with Linux having an extremely high desktop market share there relative to other markets.
I never trust stat counters of any kind with linux. I often see stuff like that plastered on my whitelist firewall, like bumper insects on a high speed summer drive through Florida. There is usually some other stat of leet users. That's Linux too. Then there are those times when I change my browser agent just for fun.
On a random note, I once talked about Firefox with a friend, and he texted me a few weeks later about trying it. More successful than my Linux spreading, although part of it was he used a Surface and having gone through the pain on my Surface Go myself, I wasn’t sure I could impart that suffering to someone else.