It's called a guts system, sort of a soft comeback mechanic. Attacks deal less damage under 50% health and it scales down up to 30% health or so
Yeah, this is what I wanted, just was not sure if it was in SFV too.
But: it is not a comeback mechanic. It affects both players equally. (And unlike with Ultras, it does not give you any tools once you "fail" enough).