Are you talking about the Musk tag used to measure visibility? I don't recall them hard coding promotion of specific accounts? Seems like it should be a major talking point.
Even if it was, that could have the same effect. If they test every change and only keep the ones that don't harm Musk's visibility that is in effect making the algorithm consider Musk specially.
Seems like that would could even be considered hardcoding - Buy Twitter Blue get higher on replies on threads.