Except as I already pointed out above, those recordings don't say "this call may be recorded." They say something like "this call may be recorded for quality assurance and training purposes." That statement is really not vague at all. It's very clear what it's intended meaning is. It pertains to the activities of the call center you've called. You have to really willfully twist the words around (or quote them out of context as you've done) to make them mean that it gives you permission to record the call.

And actually the laws, at least in the U.S., do talk about "who" is doing the recording. If you're recording, you have to notify the other party. That's what the law says. It doesn't seem ethical at all, to me, to record a call without notifying someone, regardless of whether or not they're recording the call. The point is, are you being upfront about what you're doing? Or are you hiding it and keeping it secret?

It's really quite simple. At least in those states in the U.S. where you're required to do so, if you're recording a call, you have to explicitly notify the other party. That's it. It doesn't matter what the other party is doing; that's their responsibility, but it doesn't absolve you of your responsibility.