I have to agree with you for the original Resident Evil. Which is probably exactly what Capcom thought when they made the remake and introduced Crimson Heads that spawn after you've killed a zombie and didn't burn it with your limited lighter fluid. There is a much bigger incentive to be very selective with which zombies you should kill. OG Resident Evil tried to achieve this only using ammo, but you could still just kill most zombies you encounter.

The author does differentiate it better with the second definition where combat is mandatory in my opinion. I think it fits better to say that the OG survival horror definition is that combat isn't mandatory to progress, whereas more modern ones tend to have mandatory combat.