Artificial growth hormones may be banned, but endogenous ones[0] are unavoidable. Cow's milk evolved to make calves grow, this is not an avoidable minutia when attempting to comparatively characterize milk alternatives as stunting growth, but likely the central finding.
You didn't understand GP comment. Cow's milk is the single thing that grows calves hundreds of Kg in a few months. It has growing hormones in it, naturally.
[0] https://en.m.wikipedia.org/wiki/Bovine_somatotropin