No, they mean that they control for 'career length' ... e.g. an academic with 5 years of history is likely to have a better score than one with 2 years of history.

So they effectively compare women-with-1-year vs men-with-1-year, etc. etc, rather than 'women with h-index 5' vs 'men with h-index 5'

edit: should be "Women with h-index of X after Y years" rather than just "Women with h-index of X" (e.g. they control for Y years' publishing between men and women, assuming that time-in-academia is correlated with h-index. Quick glance at the paper suggests that time-in-academia has R2 of 0.62 with h-index)