(Stated confidently to ensure a correction if I'm wrong)
Silpheed was amazing back in the day. It was one of the first titles that really showcased what CD drives could add to games in terms of cinematic experience. The live orchestral music gave it an epic feel and the mecha-design of the SA-77 is beautiful and modern even by today's standards.
The player ship rotates, but it only is 'rendered' at a handful of angles. This is a very common technique, but here they've used an art style to make it look like realtime 3d.
It's like stun runner on Lynx [1]. The Arcade stun runner was polygon based; but the Lynx doesn't have a chance, so there's just a ton of sprite options for rotation and a lot of work to make it look the part [2].
[1] https://youtu.be/4PEAzBtaStk?si=QXWf9KDUBjQRgoDh&t=204 [2] https://forums.atariage.com/topic/194231-lynx-stun-runner-3d...
Fabien seems to be unaware of this, by the way.
This is also why the game play is so bland. The number of 3d objects and their complexity was severely constrained and did not allow for varied or more sophisticated game elements.