With Musk in the CTO role, he's either going to be there every day, or Twitter is going to have an absent CTO. Both of them are bad for decision-making efficiency.

Given he is also CEO/CTO of SpaceX and Tesla, I don’t think he physically can be at Twitter every working day - unless he’s secretly cloned himself

Then he's going to be the absent (or worse, inconsistently-present) CTO, which is worse. If he's there then there's at least a chance of him and Linda working out clear roles and responsibilities. If he's totally absent then technical decisions are not going to get decided, which holds up engineering. If he's inconsistently absent then decisions may get decided when he's absent and then reversed when he shows up to the office, which makes it impossible to do any sort of long-term planning.

He obviously can't be at all three full time. Investors in SpaceX and Tesla have complained he's spending significant time in the Twitter office and neglecting the other two. Just because it would make business sense for him to focus less on Twitter doesn't mean you can assume he will - surely we can all agree, regardless of our opinion on Musk, that he frequently bucks the conventional wisdom on how a CEO should behave?