According to the Apple Developer Enterprise Program Eligibility the companies can only "Use the program only to create proprietary, in-house apps for internal use, and to distribute these apps privately and securely to employees within the organization" but these companies (Thunkable or Wix) allow to anyone export an app and install in the phone for example: https://www.wix.com/branded/apps/ios
¿Why companies like Thunkable or Wix can use Enterprise subscription to allow their customers test Apps?
Good question.
Selectively enforced?