Yeah, I don't know that I 100% agree with that breakdown, but I do think it's something like that.
For one thing, I think "flow" is a little crammed in there. I think there's reason to connect the idea of "flow" (as I understand it) to a sense of contentment, but it's probably not really about achieving the state of flow itself. At least in my thinking, I'd sooner say that regularly achieving a state of flow implies that you're good at something that you derive some pleasure and satisfaction from, and it may be the pleasure and satisfaction that is providing the psychological benefits rather than the state of flow itself. I could be wrong-- maybe he's done some studies that show my thinking is backward, but it feels like it's artificially shoe-horned in there. I do think that some form of engagement is extremely important to a healthy mental state, so I wouldn't argue with him too strenuously about it.
Similarly, I think using the word "meaning" may be conflating a couple of different things that I would tend to separate. I think that there's a kind of happiness that comes from "doing what you're supposed to" or "living the life you think you should", but not necessarily because it's extremely meaningful in the sense most people would use the word "meaning". Instead, I think a big component is something like "an absence of extreme cognitive dissonance" paired with "not hating yourself". What I intend to point out here is that "meaning" might imply things like, "saving poor starving children in the 3rd world", but many people would skip over ideas like, "I think I spent my day in an appropriate way, and I have no conflicted feelings about that." You could call both of them "meaning", but the latter is not what most people would think of.
I guess my point here is just that I think there may be quite a lot of subtly different positive emotions and beneficial psychological states of being that we don't necessarily think of when we say the word "happiness". Seligman has chosen a few, and you could argue that the others can be somehow grouped in with the few that he's chosen. If it provides a workable theory that improves psychological treatment, I'm all in favor of that. Still, my sense is that he hasn't quite hit the bullseye.
For various reasons, I would tend to favor a model that at least contained separate ideas for pleasure, joy, satisfaction, alignment (that feeling of "I am unconflicted about the appropriateness of my actions"), and meaning. I'd be open to an alternate breakdown, but positive emotions, flow, and meaningfulness don't seem to capture the range of what I experience.