Waterfall Tester in an Agile World (thought experiment)

I've been in a couple corporate worlds that are agile... well in my option, "claims" to be agile. In my opinion, most companies that I have worked for and heard from friends are really just waterfall-light or lean or wagile. My big question for today because a group just recently acquired two QA testers to join their agile group.

This got me thinking, how does QA fit into an agile group? Our testers are expected to test after devs are done developing, so how is this different from waterfall? In full agile, QA would work with developers which I have not seen any self-claimed agile group actually do (not to say they do not exist, just saying... not sure what I am saying but seems important).

TO THE MAIN POINT... (focus, focus)... I think in the agile world, testers should be a special type of end-user. An end-user that is focused on breaking the system. When they find a bug, they report it like any end-user. Simple, clean, and feels like a nice sweet spot.

There is a little nagging feeling on this in that "isn't this testing in prod?" If we trust the agile methodology, this should not be a major concern. Small changes should have small impacts. By small change, I mean a change that has little impact. (Is that a catch-22?) What I want to say is that, there can be physical small changes that have big impacts. For example, a piece of code that is heavily coupled with almost everything, like security or audit or logging.

How does agile test those conditions? I don't think there is really any agile-method besides really falling onto a more waterfall-method. Which is also one of the reasons that I always shudder when I hear leadership say we need to go 100% agile. I may not know agile enough, but doesn't the first 30 minutes of agile training basically make that impossible unless the company really has absolutely no idea what it is doing? I mean, we have full spec'd out requirement that has been done multiple times... and you want to make that agile too?

I've been in two waterfall to agile transformations, and I've seen processes that took a couple days that are now two weeks because they need to go through more steps. Yes, agile should address this but don't like it when it becomes more waterfall so... yea. I tried... again... and again... but at some point there are more important things to fry and technically it adds more job security for my role. People look at me weird suggest something that does not really benefit me personally.

Anyways, if I ever have my only agile team and was assigned QA testers... I would have them help with writing test cases then test things in production. Bugs/issues will just go on the backlog and treated in an existing process.