@Fushiadreams
No, it's apples to apples. Nutshell version, all our earnings are of overseas origin (USD), distributed half US, half UK. (As US citizens and settled status UK payers) total income and timing of payments matters, where an asset is held made no difference as soon as we went from non-dom to settled.
Exemptions are pretty simple as they're contained in the US/UK tax treaty. Granted, I don't know if this is differently applied to non-US citizens (and where/how green card holders fit in). I also don't know where Ms Murthy was paying tax on her holdings previously (they weren't particularly transparent on that), so don't know what kind of treaties are or are not at play there.
Double taxation would be an issue if she's at the top of a C Corporation, I believe (which is why most people in her position would structure as an S Corporation) and while it's not total double taxation but some aspect of that for capital gains (for which the UK reaches into worldwide holdings).
Either way, my heart's not bleeding for them, and I think considering the amount of money they have, and the position he's in, it's not a good look.
I also, as I said before, don't buy the totally separate finances thing. We have certain investments neither of us can make due to the creation of a conflict or interest for the other. There's no way they haven't been in this position.