Yes, the housing and t-stat are sold as both a unit and separately. The unit is much easier to install rather than having to put it together yourself and installing. If you buy them separately, you'll need to purchase the O-rings as well. Bear in mind, most t-stats are manufactured overseas and are assembled in the housings here. The price of t-stats has almost doubled- I know, I've replaced mine 3 times in 10 years. Tariffs and whatever....
I installed this one just about 6 weeks ago from Parts Geek: