It's a pretty common question, so I'll lay it out here for anyone that's wondered the same. Long response here, so only read if you really want all the details.
Firstly, there is a difference between a glitch and an exploit. The definition can vary somewhat, and the line can be hard to define in many cases, but in general I like to think of a glitch as the game behaving in a way that should be impossible, and an exploit is using things that are intended to create an unintended interaction.
Skipping the Chained Ogre completely is a glitch because there is a fog wall that's supposed to make that impossible. Circling around Ogre so he basically never gets a chance to attack is an exploit because it probably wasn't the way the developers intended for you to defeat him, but everything in the game itself is working exactly as intended. His AI isn't broken, he's still trying to face you and hit you, he's just programmed to not use an attack if you're behind him and his turn speed is rather slow.
So lets look at the example with Genichiro. Is he intended to be able to enter that corner? Yes. Is it intended that you can attack while unlocked from an enemy? Yes. Is it intended that an enemy won't block if you're facing away from them? Yes. Is it intended that your sword can hit an enemy even if you're not facing them 100% dead on? Yes. Is Geni's AI still functioning and trying to attack you? Yes.
So really, there's no part of the interaction at all that's broken or glitched out in any way. It is entirely intended actions, we just happen to string them together in a way that doesn't allow Geni the opportunity to attack back at us. The purest definition of an exploit, in my opinion.
Besides that distinction, let's presume that we did call it a glitch. What would we ban?
You can't have him in the corner? Then if you're fighting and he just happens to back up into the corner, is your run invalid or do you just have to wait around until he leaves before you attack him? Besides, you can still use the "deadangle" exploit in the middle of the room, we do that on his lightning phase as well.
You can't unlock during the fight? Would this apply to all fights, so you can't fight chained ogre unlocked either? You can't unlock to hit headshots on Guardian Ape? What if the unlock randomly breaks because the camera gets stuck on a wall? It would be a very silly rule in my opinion. Plus the interaction of hitting an enemy unblocked while locked on still happens. It happens often on Geni, but it's very obvious on a boss like Lone Shadow where your attack can just go around his block randomly in some rare cases.
You can't turn away from an enemy? Basically the same objection as unlocking, it would be very silly and very hard to enforce.
You can't hit him unblocked more than x number of times in a row? There was actually a bounty that had that exact rule, and you could basically lose an entire run if the enemy just decided not to block at all. Geni will sometimes, even while locked on, let you hit him over and over again. It had some interesting strategies to avoid that happening, but it's a very arbitrary rule that wouldn't make sense for main speedruns.
You can't combine all of those things together in that exact corner in exactly that way? We'll find a new corner to do it in. Or we'll do it in the middle of the room. Or we'll only hit him 3 times in a row then stop and restart. Or we'll circle around him like chained ogre, or we'll do turnaround deadangles, or whatever else is fast.
When the goal is speed, you need to make clear distinctions of what is and isn't allowed, and just banning one particular way of doing something will just lead to other ways to do it. If I ban one single jump that skips a boss, then other ways to skip a boss can just be found. You need to instead ban skipping the boss period, no matter how it's done. And there's nothing here that could reasonably and clearly be banned.