@Oli ******
"Tax Residency" has nothing to do with actually paying taxes. It is simple the point of residence where you would be taxed if you had to pay taxes.
I am tax resident of Thailand. But have no taxable income. So: I do not pay taxes here.
And I am no longer a tax resident of Germany: so I do not file income tax declarations there.
And not that is not a theory (correct word would be hypothesis, btw): it is law, since a half a century or longer.