This is weird stuff. The DH is out to work all day - some posters are mentioning hard physical jobs but some office jobs, even highly paid ones, aren't all that stressful - and then he comes home and shouldn't have to lift a finger. That's nice. Meanwhile some of us don't have a SAHP so we go out to work all day and then come home and have to do the chores because there's no-one else to do them. Not dead yet on that level of demand. It may not be unreasonable to expect the SAHP to pick up the majority of the daytime chores, and indeed the OP says her SIL does do that, but expecting the WOHP to do a bit when they get in is hardly unreasonable either, under most circumstances.
I've also grumbled about this one before, I'm sure, but: the number of remarks on the lines that housework doesn't take long. Well it depends, doesn't it? My mother, for example, was a SAHM in a large old-fashioned house, five bedrooms, two bathrooms, three toilets, with lots of nooks and crannies; it was not at all easy to keep clean. You may be able to run a vacuum round a two-bed flat in five minutes, but it took her nearly that long to lug the (large, also old-fashioned and not very efficient) vacuum from one end of the house to another. Some of the rooms took over five minutes ffs, by the time she'd shifted the furniture round and picked up all the stray tissues etc that some thoughtless offspring had dropped behind it.
She didn't drive, and we lived about half an hour away from the school, so there's two hours of her "free" time every day just used up taking the DC to and fro. There were no nearby supermarkets so she would go to town on the bus to shop, some forty minutes each way as we weren't that close to a bus stop, and lug a wheely basket and a selection of bags home on the bus again, sometimes including a pram and/or wrangling a todddler. She wasn't half grateful when I learned to drive!
We had a huge garden and only my dad was capable of starting his horrible old petrol mower (actually even he used to struggle with it), so my mother would mow one lawn at a time with a small hand mower - we had three lawns in the front that are larger than my whole garden nowadays, and a much bigger one in the back, and more flower-beds than you can count; it wasn't Kew Gardens but it was a very awkward layout.
Fortunately, although old-fashioned in a lot of ways, demanding, and temperamental to an extent that would be considered abusive nowadays, my dad was a meticulously tidy person, did not leave a mess after himself, ironed his own shirts, mucked in at the weekend, and insisted that we did not make life harder for our mother than necessary. She was still pretty frazzled at the end of her "pampered, non-working" day.
So, as I say... it depends.