prone to MPB and using steroids does not necessitate people will notice they are losing hair. the vast majority of men are losing hair, naturally, on a day to day basis and steroids will simply increase the extent of their daily hairloss, to a level which is unnoticeable to the naked eye.
should be worth noting how often people claim their hair regimes are working and what not, even though it's mostly placebo effect. the only time people even say they lose hair from steroids is when they have a shed, which isn't even an accurate way of gauging MPB, and is different type of hair loss.