I couldn't find any information regarding using two primary buttons on the same layout. Not any research or scientific justification.
In my opinion, this is weird and doesn't give the user enough information to make a selection. If it doesn't matter to you whether the user clicks one or two buttons, then why are you adding both?
As with all UX, the most important thing is to ask questions. Why do we need a second button? Which option is preferable for us and which one for the user? If we decide on this, then we can understand how best to show it to us. And if the user still shows good results after testing, then we can safely write an article "justification for using two primer buttons at the same time"))