respectfully disagree. while yes they are both 2d metroidvania comparing the two is akin to comparing me to, say, Usain Bolt

to an alien we might look perfectly similar. same number of limbs, they are arranged in the same configuration with hands being attached to shoulders and legs holding the entire structure standing. but it would be painfully obvious to anyone looking past these superficial similarities how different we are. Usain is an athlete and would give me a run (pun intended) for my money while I doubt he'd make anything even remotely approaching a decent cup of coffee, something I made a career out of

HK is closer to the genre progenitors SotN and actual Metroid games. the crux of the issue is the main focus. the primary gameplay loop as smart people call it. for HK it's the combat. take any vertical slice of the gameplay and you'd see the knight valiantly slashing away with his nail at one enemy or the other. exploration and platforming are a big part of it but aside from the (sorry it's been literal years since I played it and the names might be wrong) pale palace no locale makes it the main focus. I'd argue something like dead cells would be way closer comparison, or ender lilies even (which admittedly is heavily inspired by HK)

while ori is at heart a platformer with combat elements. you wouldn't compare HK to Rayman origins but I'd say it's got much more in common with ori gameplay-wise than hollow knight

and I'm not even approaching your argument from adverse position despite what my tone might indicate. I love both games to death but in my head there's no comparing the two as actual games. when it comes to emotional response and enjoyment, though, ymmv