Yeah, but that's kind of the thing, you get less battle testing most likely for also less surface area. If you pull in a project like this, it makes it vastly easier when you need more, because if it happens to already have built-in support, you don't need to spend additional engineer time on it.
To me it seems straightforwardly a win to start with Testcontainer and move to something else when it proves insufficient.
The effort would not be equal to replicating the whole project. It wouldn’t be the same quality of course. Question is do you need all of it or not.