It's a really interesting debate.
I am the higher earner in our home, dh works ft and I work pt (have Fridays off). Dh is a great bloke, hands on dad, does fair share of drop offs, pick ups and household chores etc (sometimes needs reminding). My job is pretty high pressure, lots of stress, in comparison to his (which he freely admits). I do however wfh, but invariably on back to back calls. I do all our life admin, and thinking/ planning ahead (e.g. sandwiches for kids the following day, childcare arrangements etc).
Yet still he persists in asking me, every Thursday evening, "so, what are your plans tomorrow, what's on the to do list?" There is still an underlying expectation, even in quite an egalitarian relationship, that I will fill every minute of every day with productive activities for other people. Wife work. I've called him out on this recently. Actually dh, Friday is the one day of the week when I actually get to exercise, so I swim in the morning. I then catch up with anything else the family needs in terms of life admin and house chores so we can enjoy our weekend together, I eat lunch and then it's time to go to school to collect the dc.
The thing is, no relationship or family circumstances are the same as another. Ours works pretty well on the whole but isn't perfect, and I suspect many others - whether sah or woh, or mixed arrangements - are the same. The only time I feel compelled to offer an opinion on someone else's situation is when they invite the discussion by posting on here and things are so obviously out of kilter that some advice might help them readdress the lack of balance in their lives. In real life, I've never come across the sah/ woh snobbery. And I do agree that it tends to be women who are still having this argument with one another when in the 21st century, men are perfectly able to pull their weight if they are willing to.