It prevents further masculinasation, rather than femiize.
Since feminize just means, besides the pelvis and face,
less bone thickening
(T's has the effect of making the bones more robust, increasing
their cross-section),
part of the bone thickening is due to not just T, but the effect
of the muscles on the bone's attachment points. Especially
apparent on facial bones.
The thickening effect occurs well past lengthening
and growing effect (driven by estrogen even in men),
it has an effect up to the late 20's.
So, stopping T early means a more delicate, if not smaller, ossature,
except in the face, where both an increasing ength and robustness
continues up to 30 due to the bone plates never quite fusing.