It's possible that those teas you are looking at are funky herbal concoctions with various "artificial flavors" and things added as well. There's a lot of weird stuff out there.
First thing: Tea properly speaking is made from the tea plant, camellia sinensis, and comes in three basic varieties: black, oolong, and green (with white thrown in there as three and a half). These are all from the same plant, picked in pretty much the same way; they differ in what happens to the leaves after they've been gathered. Basically, the difference is in the degree to which the leaves are oxidized, with black treated the most, green the least, and oolong in between. (And white tea is not really altered at all.) Tisanes are the herbal concoctions: peppermint tea, chamomile, tilleul (linden tree flowers; common in France I gather), lemon, etc. These are loosely referred to as "teas," but the industry calls them tisanes, just to be clear (or snooty).
In general I think you will more often run into weird stuff added to herbal teas than to real tea, but it still happens in the latter case. In scented or flavored black teas, for example. But you can find good, clean sources for herbal teas just as you can for tea. The company that has pretty much become the gold standard for tea in the United States is Harney & Sons. It's a little pricey, but you can get big 50-count boxes of teabags for a decent price, and I assure you that you will not be disappointed. And if you want herbals, they have those as well. You can get a looseleaf chamomile for instance: it will be a tin filled with chamomile flowers. As easy as that, no other ingredients, and delicious. They also have organic teas, if that's your thing.
We've probably heard of those claims that green tea can improve insulin sensitivity (here for example). And we also think as paleos that "oxidation = bad" and so green tea is surely better than black tea. (Although of course there are no lipids in there.) But I never reacted well to green tea. One of the things I read back when I was spending a lot of time thinking about tea was that although there is technically less caffeine in green tea, the caffeine that is there is more "available" to the body, and so ends up having a greater effect on one than black tea does. There could be something to this. But I also found, as the research findings about green tea improving the action of insulin might support, that green tea just makes me hypoglycemic. I don't know why, but it does. (Well, black tea and coffee do also, if I'm not having them with food, but green tea is worse.)
People react different ways to different things of course. But this should give you some things to think about if you are engaging in some regular tea drinking.