This is a little unusual. Most games never explicitly say you need an SSD or a HDD - but Starfield does! This likely isn’t a hard limit, as recommendations are often just that, but I cannot help but wonder what would happen if the game is run on an HDD?
World of Warcraft has an SSD requirement since the last addon. It still runs of HDD but the loading times aren‘t fun. Also I‘ve seen multiple cases of texture- and other pop-ins. I would suspect similar problems with Starfield. Skyrim also had many problems with pop-ins (with mods even on SSD) and I somehow suspect that Bethesda didn‘t really improved on that end.