What is a Guard

So, I know the classes mostly don't matter, and it's more important mechanically to pair characters in teams by what they *do* rather than what the game says they are. But it's really bugging me that I think all but one class has a pretty clear, consistent identity. Like, Striker - Melee damage. Pretty clear, generally seem to be built around stacking up a bunch of inflictions/vulnerability and exploiting it. Makes sense. Caster - Ranged damage. Tends to cause inflictions/reactions rather than exploit them, but like Striker is primarily focused on damage. Defender - Tank. Defends. Provides counters to enemy attacks, shields, a little healing. Straightforward. Supporter - Supporters. Not really more complicated than that, buffs, debuffs, healing. All ranged characters right now though not sure if that's inherent to the class concept. Vanguard - SP-based Support. Generates and refills skill points, provide some buffs, some infliction, some reactions, but their primary job is to let you cast battle skills. And then there's Guard. We have four guard characters in game at current - Endministrator, Chen, Estella, and Lifeng. The in-game description says that Guards are "skilled at making enemies vulnerable and applying physical statuses" Which is technically true, all of these characters can apply vulnerability, even Estella despite being a Cryo character. But like... so can Da Pan. So can Pog. So can Ember. So can Gilberta. So what's defining Guards? Can they apply Vulnerable more than other classes... Kinda? Chen and Estelle can for sure, I don't have Lifeng so maybe he can but I don't wanna say definitively. And the Endministrator kinda can't? Are they meant to be physical supports? It seems like kinda? Weird that Pog isn't a Guard if so, but he has SP stuff so vanguard does make sense for him. But like, Estella works really well for enabling a Solidification team, and doesn't do a lot of personal damage, so sure that fits. Lifeng is obviously built entirely for phys support, okay. But then Chen... I mean what makes her a Guard compared to Da Pan? I guess she doesn't have a way to *exploit* Vuln, she can only apply it with Lift. Okay, maybe. But the Endministrator *does* exploit Vulnerability, they are *primarily* a damage dealer. Why aren't they a Striker while Da Pan is? Am I missing something? Again I know it doesn't *really* matter, but I kinda like this game's classes and think they're otherwise pretty well-defined and clear indicators of what sort of thing a character is for, except Guard. tl;dr, Guards feel really ill-defined because 2/4 characters are focused on dealing damage, while the other 2 are focused on support. And there's nothing super defining that connects them.