It's neither. I don't agree with Musk's politics. But I do see where this explanation is plausible. When a US military grade service is made available to non-allied countries (Ukraine is not a part of NATO), there are always end user restrictions that the US Government will maintain control over. This is not something left to Musk. Someone from the department of state or department of defense (well, war at the moment) will control it. Those restrictions are subject to executive orders and changes in US law. This is why countries that don't align with the US (e.g. India) don't want to buy advanced US tech. It is better to have a sub-optimal system without end user restrictions instead of a cutting edge one with too many of them.

Trump calling Musk to not do it is just reality theater. Someone from the executive chain of command ordered this.

Remember the Iran fiasco has diesel prices being sky high. There's an election around the corner and Russian oil is needed to stabilize the prices. It is Ukraine's right to strike Russian oil assets, but if they're using US military tech, US interests will control how it is used.