EPRB and independent vs dependent variables

thray wrote:… a variable cannot be both dependent and independent at the same time.
Tom, not wanting to sidetrack other threads:
Let Xi + Yi = 0, (1)
where Xi and Yi (hidden random-variables in EPRB; i = 1, 2, …, N) are pairwise correlated by the conservation of angular momentum.
Alice can choose Xi as the independent variable, so Yi is her dependent variable.
Bob can choose Yi as the independent variable, so Xi is his dependent variable.
So: Do we need to qualify your --- "a variable cannot be both dependent and independent at the same time" --- by saying: the notion of dependence or independence is reference-frame dependent?
Tks, Xray