Surprising US tax treaty rule

As a US resident  & occasional UK dual resident I have been lurking and occasionally posting here for a few years, learning how to plan for future tax issues. I thought I had a reasonable handle on my future UK taxes, Roth conversions etc as a dual resident subject to multiple taxation with treaty relief - until now....

Well, a few days ago I reached out to PJT Tax with some questions and was truly floored by their response!

Essentially, they said that as a US treaty resident, that determination overrides any UK residence from Statutory Residence Test (SRT) such that I only pay UK tax on UK income rather than worldwide.
This was a shock given I have had conversions with at least three other so-called ‘international tax experts’ over the years who all omitted this crucial info.

Perhaps I am the only person to miss this but I suspect I am not,  so here is the relevant info below.

link provided by PJT Tax
https://www.gov.uk/hmrc-internal-manuals/international-manual/intm154020

from the linked page
An individual who is ‘treaty resident’ in the other country is entitled to make claims to relief from United Kingdom tax as provided for under the agreement on the basis that they are a `resident of’ the other State. As a result:
•  Income or a gain of a type which is dealt with in the agreement and which arises in the other State is always exempt from United Kingdom tax.
•   Income arising in other overseas territories is exempt if the agreement has an `other income’ Article.
•   Only UK source income can be taxed and then only to the extent that such income can be taxed in the hands of a sole resident of the other State. Special rules may however apply where any income (including foreign income) is connected with a business or profession which the individual carries on in the UK.

That’s nice if you can afford to maintain homes in both countries.

That’s nice if you can afford to maintain homes in both countries.

This would also apply to anyone from US taking a long holiday in UK. If you have family in UK and spend 4 months in UK then you become 'resident' - if you spent 90 days in UK in either of previous 2 years then the trigger is reduced to 3 months.

With so many HMRC and treaty docs discussing dual residence and and how to deal with dual taxation, I thought I would have to deal with it too - hence my surprise when told that I would not.