That’s effectively true for at least the lightning. It’s possible that volumetric lightning data for a whole area is preloaded into the sim, but it only uses one value at a time from where the aircraft is located. This results in a weird effect: If there’s one lightning producing cloud in the distance and “ambient thunder probability” is >0, you’ll see lightning flashes from it. But if you fly to a new location where that parameter is 0, that same cloud will stop producing lightning. It’s like you control the lightning simply by where you’re located.
I’d love to hear more about how this applies to other weather in the sim though. Are you saying the clouds are randomized based on the player’s position? So for example, two players won’t see the same clouds when flying together in multiplayer if they’re coming from different areas?
Edit: Ah I see the thread now: MSFS2024 is randomising the positions of the clouds for each person that spawns in - #2 by MSGamerTag01