Who gives a "FIG", UK's Foreign Income and Gains regime and US SS

So new UK residents who have been non UK resident for the previous 10 years can claim UK tax relief on their foreign income for 4 years. This seems to include foreign Social Security payments as "Qualifying foreign income".

https://www.gov.uk/hmrc-internal-manuals/residence-and-fig-regime-manual/rfig45100

But the DT treaty reserves the right to tax US SS when paid to UK residents to the UK and it is exempted from the "Saving Clause". So has FIG created a possible 4 year window when US SS payments paid to UK residents are tax free? I'm sure there will be some language that will require the US tax to be paid, but it's an interesting scenario.

I’ve wondered about that as well.

I’ve wondered about that as well.

A little Googling comes up with the concept that the treaty is the "supreme document" and even though HMRC states that foreign SS is FIG qualifying income they effectively exclude it and tax it. This does not surprise me as in taxation I've found that there is "no free lunch" and it can be dangerous to believe what you read.