This is somewhat but not entirely true imo, from my experience working part-time.
A lot of the workload with young kids is just "churn" - change nappy, make food, clear food away, get out craft stuff, do craft, change nappy, tidy away, make snack, clear away, get out toys, clear away, make lunch, clear away, change nappy, put on coats, outside, back, put coats away, make food, clear up spills, wipe up mess, change nappy etc. So if someone else is looking after the kids, you don't have to do it. And the house doesn't get messy in the way it does if you're in it all day.
But then alongside the "churn", if you're at home with young kids, you do sometimes have a chance to crack on with other jobs that would need doing anyway like laundry, hoovering, tidying, cleaning bathrooms, cooking etc. in the time you would otherwise be at work.
So there's a partial benefit there but it depends on how much the "churn" overwhelms you.