Why wouldnt they be subject to SE taxes in the US?

If you are a self-employed U.S. citizen or resident, the rules for paying self-employment tax are generally the same whether you are living in the United States or abroad. The self-employment tax is a social security and Medicare tax on net earnings from self-employment.

https://www.irs.gov/individuals/international-taxpayers/self-employment-tax-for-businesses-abroad#:~....