[Tobi Grüner] FIA is trying to close budget cap loopholes. We explain, how R&D and production costs can be removed from the books using "external" companies and how supercar projects could be misused
I think it's targeting projects like the AMG One and the Redbull one. The WEC entries have a different set of regulations.
In the article it says:
With a Le Mans hypercar, like the ones Ferrari and soon Alpine have, that's not possible. There are regulations for that that have nothing to do with Formula 1. It would be conspicuous if Ferrari were to screw an underbody under its 499P for testing purposes that looks similar to the SF-23. Ferrari would have to go the same way as Red Bull via a customer sports car for the racetrack.
Ah that makes since yeah, they are selling those to customers though, would suck if they were forced to stop making a real car because it helps them make a better track only car