Nobody has ever said anybody should be spending 8 hours on housework, they have said that they spend 8 hours caring for a baby on their own, and that that counts as work.
Some days you get the laundry done and some errands run, other days you don't.
And what those days are will depend a lot on you, and a lot on your baby.
But the point is that there should be no expectation that a man should cease having to do housework just because his wife is on maternity leave.
It's not skivvy leave. There are people who seem to believe that as soon a woman doesn't leave for work in the morning that she has reverted to a time when women were forced out of work as soon as they got married and when it was acceptable for unmarried women to earn a fraction what was paid to men doing the same work.
Just because you are at home doesn't mean it is your job to run the home.
I value my time way too highly to spend it running about doing jobs for a man who is more than capable of (and happy to, in my case) look after himself like a big boy.
My maternity leave is for me and my baby, not for DH's benefit so he can not bother his arse doing any work at home (not that he is that lazy, he takes pride in doing his bit to run our family). It's still easier for him when I'm on mat leave, because I am more flexible and can run errands, and some days I will get tons done in the house. But that just means that when we are both at home we get to other jobs that need doing that we rarely have time for.
Every evening DH and I come home from work, one cooks, the other tidies up the kitchen, loads dishwasher, one or other of us tidies the living room of toys. It's hardly some big imposition to have a few light chores to do when you get home from work. There's still plenty of lounging about time if you're of a lazy disposition.