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?
SSDs have been around for a long time, and have been affordable for quite a while now. While optimization should always be happening on the developer side, its not crazy to start requiring 30+ year old technology to use modern games.