I don't have a metered home internet connection, but 
, who is this for?
Are they streaming textures?
People who get really in to flight sims are often very dedicated hobbiests who end up with a pretty wild array of specialized equipment and peripherals just to play. As the article says, what the game is streaming in is immense amounts of geospatial and photogrammetry data - aerial and satellite images processed to provide detailed 3d maps of the real world for the player to fly around in. It sounds like they might be getting in to wacky things like real-time weather modelling, too, which... woooooah.
Real time weather has been in MSFS for a while if you want to turn it on, there were a ton of clickbait videos on YouTube about flying through hurricane Milton or Helene over the past few weeks.
People were flying in tropical cyclones when MSFS2020 came out (in the middle of north Atlantic hurricane season), too. I'm guessing the live weather data might have higher fidelity or something in 24
This is generally how these things work. MSFS global scenery is a large number of terabytes in size. Local scenery is streamed on-demand as you travel around. Very few people would have the means to store it all locally. MSFS isn't the only flight simulator which does this. FlightGear, a free software flight simulator uses a system called TerraSync which does the exact same thing, however the scenery tiles in FlightGear are rather modest in comparison (in the upcoming "World Scenery 3.0" terrain system, the state of Colorado consumes 513MB compressed).
I'm guessing it must have some kind of cache for people that don't have absurd internet connections. I never got too into scenery packs and extra data for MSFS2020, but I'd usually just focus on a single region at a time with the freebie packs MS put out.
As someone who deals with lidar and other geospatial data for work, this tracks. A scene the size of a small town can be gigabytes in size
Flight sim is probably the most expensive PC game category except from maybe whaling in certain games for lootboxes.
A large storage drive is a given for most, even sometimes dedicated drives and its not that expensive these days. It realy isn't 2000-10's anymore, storage is incredibly cheap now. Have a main OS SSD + 1 dedicated storage HDD is a given.
My experience with XP11 is that the barrier is the knowledge and dedication to do custom scenery(ortho) compared to what MSFS gives out of the box. You're paying quite a premium for MSFS's convenience and massive coverage.
