What? You think having strangers in your own home commanding you to do what they tell you over video conference is unacceptable!? Sarcasm aside, gig-to-hire arrangements would go to the top of the heap when it comes to prioritizing opportunities.
Would you allow junior developers to whiteboard a highly qualified and accomplished CTO candidate? No. It is acceptable for peers who will be competing with the candidate in the promotions tournament or the hiring managers to conduct whiteboarding exercises.
When I was self-studying social psychology I came across social facilitation theory and found it applicable to understanding interviewing. People have a hard time performing complex tasks while other people are watching because their working memory is monitoring the social situation. This varies for each individual. For tasks that have been rehearsed, like a musical or dance routine, they perform better. Politeness theory is applicable as well, people want to be liked and at the same time do not want their autonomy challenged. My pet theory is that the whiteboarding epidemic is a status hierarchy game essentially communicating "if you want to work here, you are going to do what I say."