You walk into a tea shops and find countless varieties. All those herbal teas: not really tea. They are made from non-tea plants, most of which taste nothing like real tea. Peu-er is probably as close as it gets.
The remaining (real) tea all comes from the same singular specie. Green and black is just a difference in processing of the same plant. White tea is just taking the tips of the tea leaf. All the flavors are just ways we dress it up with additives, or by smoking it (e.g. Russian Earl Gray).
Why the lack of biodiversity? Because no one has genetically modified a tea tree to give us more choice. There are far more tea drinkers in the world than coffee drinkers. That’s ideal b/c coffee has environmental consequences. It also means there should be a huge market for something like a tea tree that is married to a maple tree to give us maple tasting tea, or GMO tea that tastes like coffee.
The phrase “tea tree” generally refers to a different plant than Camellia sinensis. “Tea plant” or “tea bush” are what you’re looking for.
Tea is just one Camellia of many. Tea seed oil is used in cosmetics and comes from a different Camellia and ornamental Camellias are common in gardens around the world. Your scope on Camellia doesn’t encompass the breadth of it.