I never said you said that.
Both jobs are NOT equally stressful. Not even close to equally as stressful. I'll use My job and my wife's SAH-ness.
My job is mental stress. Mental stress is not equal to the physical stress mary faces 'doing' for our daughter in the mornings, and our son during the day. There is 'some' mental stress, but very little. She faces emotional stress when the kids 'get on her last nerve'. When that happens she sends them to take a nap. I face emotional stress when 'the person who controls my family's income' gets on my last nerve. I cannot send her away, to nap.
I have to be at my desk at 6:30. I have to remain in this general area until 4pm. There are times when I have nothing to do but post here. There are times when I don't have time to take a break to pee. My wife has to get my daughter ready for school, and have her out the door by 9am. If my wife wakes up at 7 or 7:30, or even 8 she can get that done. After my daughter leaves, she does whatever the hell she wants, when she wants to. If she doesn't 'feel' like doing the dishes, she doesn't 'have' to. Our lives won't change by her failing to meat goals or complete projects. If I don't complete enough projects in a row, I will lose our only source of income. She has a level of Autonomy I'll never have whilst slaving away, for TheMan. She controls the situations around her, while there. If she gets stressed out beyond reason, she has the power to put the kids away, open a bottle of wine, and relax. Last time I tried to take off my pants, kick back and enjoy a good cab-sauv at work I nearly got fired.
All sources of stress can be overwhelming. Those sources are not equal, however.