From what I’ve read “lump-sum” is not well defined in the US and open to interpretation. In the US the 25% is can be interpreted as a partial distribution not a lump-sum whereas lump-sum would be 100%. There are a online blogs arguing both sides of the coin.
Agreed, the irs letter is an interpretation not a ruling, however as it’s close to tax day I’m not pursuing the treaty now but may file an amended return later. I would still need assistance completing form 8833 as the tax attorney was not interested in helping me - “too much liability”
