I mean I think they do have some play testers for new EPs (and their corresponding updates), but I do not think they do for laundry list type updates.
I do not play with a lot of script mods (and if they made these features I wouldn't need them!). I have way too much time on my hands, I am finding bugs, and internal file errors on my own pretty quickly. I am only missing 2 EPs and 3 GPS (which I really don't have much interest in getting), but only have a few SP/Kits. So I have a good portion to test with, but I swear every ticket I post (some are years long known issues if you google it, but yet non-existent if you search the forums), they don't get the upvotes. So if you want a tester for the more obscure issues, and errors—I might be able to help XD
But I feel generally, although they claim their devs actually play the game, that they really don't play like the rest of us, the majority, or the addicted/obsessed.