An SSD will not raise your frame rate, but on a big open world an old HDD can wreck load times and asset streaming while the FPS still looks fine. Storage is a real problem, just a different one.
Put GTA 6 on an SSD or NVMe drive, not an HDD, that is the baseline. But do not expect it to fix a weak GPU or CPU. If the check flags graphics or processor first, fix that before touching storage.
Do not buy on a guess. Check your exact setup in 60 seconds and see the one part that matters.
official:Rockstar Games GTA VI page. Rockstar lists GTA VI for PlayStation 5 and Xbox Series X|S. FrameReady does not treat PC requirements as official until a PC source exists.
predicted:FrameReady Can I Run tool. FrameReady uses predicted PC targets until official PC requirements or measured benchmarks are available.