Interesting question and one I've never thought of before. It might depend on the species or hybrid. I took a look at my currently blooming Masdies and most do look like they're blooming from new leaves, but then there's floribunda. That one has so many flowers coming from everywhere on the plant that I can't believe they're all coming from current years growth.
It might also depend on when the plant lost most of it's leaf. If the flower or spike was already developing, it might not impact the blooming.
I really have no clue and should go eat my oatmeal now.