I personally was confused for a while why the explanation was increased mineralocorticoids when 11β-hydroxylase deficiency would decrease aldosterone synthesis. May be helpful to add that the hypokalemia is due to the mineralocorticoid and aldosterone-like activity of 11-deoxycorticosterone (DOC).
source: AMBOSS
https://next.amboss.com/us/article/W40PRT?q=11%20beta%20hydroxylase%20deficiency#7HY47q
under "Diagnostics" in the table -> "Hypernatremia, hypokalemia, and metabolic alkalosis are due to the mineralocorticoid and aldosterone-like activity of DOC (see “Pathophysiology” above)"
card Anki id 1586033838302 also states in Extra section that "11β-hydroxylase deficiency leads to increased mineralocorticoid effects due to increased 11-DOC which is a mineralocorticoid"