My opinion is that most see through the facade. Such as the ridiculousness of the current Red Bull Tag Heuer engine. We all know it's a Renault. Tag Heuer makes watches not F1 engines.
Even if badged as a Nissan, we know it's a Renault. The only exception in my opinion is if you brand them all the same. Such as VW has a slew of brands. They could assemble an engine design team from various parts of their empire or even outsource a full design and then decide to badge it as they like... Porsche, Audi, etc. Not that I believe that is how VW would do it, but I just use them as an example.
The other alternative would be if there was something different other than the name printed on the marketing material. For example if someone in the larger Fiat domain used the Ferrari engine as a basis and made their own unique version. But given the complexity of the engines today, that is an unlikely path.
Richard