That's a very good point. This seems to be a major point against an explanation based solely on encouragement/bias.

In a solely encouragement/discouragement based theory, it might be that for some reason, males are encouraged as well as discouraged more strongly than females. I don't know of any (even anecdotal) evidence of this happening, so I wouldn't bet on it.

In any case, the underlying origins of these statistics are no doubt complex, messy and controversial.

Males are not a homogenous group. There's no reason why some subgroups of males couldn't be negatively affected by social pressures just because other subgroups are positively affected.

Male nurses is probably the most glaring example of that.