Is the following sentence equivalent to $\sf AC$ over the rest of axioms of $\sf ZF$?
For each infinite set $X$: if for all $y \in X$ we have $|y| < |X|$, then $| \bigcup X|\leq |X| $?
Note: The cardinality function $||$ here is defined after Scott's.
If not, then to which of the known choice principles this is equivalent to?
This comes in connection to this question.