Not sure this counts for Nebula. Font licenses (even very liberal ones) are a massive pain and expense for content creators who publish to multiple platforms in a variety of different mediums.
Collectively their creator/owners will be paying thousands of dollars/month for their fonts. Something you’ve correctly assessed that a very low number of their viewers will notice or care about.
Nebula can make one upfront payment (likely less than a single months font foundry payments for their owners), and give the creators absolute certainty that the created font is free forever, no matter the viewing platform or medium.
Seems like a decent place to allocate some idle cash.
Plenty of fonts with the same SIL open font license around already, especially if what you're after is a nice but generic modern sans serif font which 99% of users can't distinguish between.
Can't think of any reason why Nebula creators would go for this one other than to blend in with the platform's corporate house style for the 1% of users pedantic enough to notice and... well they could have picked an existing SIL open font for that if it had been about simply minimising creators' costs
I'd understand it way more if they were a big corporate creating something very distinctive and very closed source for their marketing material...
Judging from the kind of content creators nebula hosts I'd imagine they do in fact have the kind of nerdy audience that notices miniature font differences.
In some ways I feel that caring a lot about fonts is on the opposite side of the spectrum to whatever it is making a population feel their lives have more meaning during wartime or crisis.
As a visual designer, sure, it is you job. As a computer user whose ultimate goal of using a computer is something else... I am kind of an old fart, but I often find that the best content is often found in conjunction with "font-family: sans-serif".
I'm a mechanical engineering PhD who works on numerical computing, data analysis and the like. I've spent several hundreds of dollars on fonts. Because I like things being just so, because I like seeing the artefacts I produce being nice to look at, and because they're just plain beautiful.
Day to day, I use open source fonts that Butterick recommends. But once in a while, I like using just nice stuff. It's like a nice fountain pen for others.
As an example, Tantacrul made a video about developing a sheet music font for Musescore (https://www.youtube.com/watch?v=XGo4PJd1lng)