A visiting engineer from Japan was asked "What do you do on the weekend at home?" He replied "What weekend? A week at home is Monday-Tuesday-Wednesday-Thursday-Friday-Friday-Friday"

I don't understand? Can you explain what that means?

He means that instead of having a weekend, it’s like three Friday’s in a row, ie they work the weekend.

6 days a week working 9am to 9pm? When do they go to the grocery store or even have time to spend at home?

Perhaps they're more likely to have traditional family roles? Leaving aside extended families, I'd find it hard to imagine that a nuclear family unit could sustain both adults working a schedule like that.

This is very true. The 12 or even 16 hour workdays we hear of in the early industrial era in the West seem incomprehensible. Until you realize that the factory complex was essentially their whole life and community. Don't need to walk far to work, or go shopping, or spend time cooking, when you live on-site in the dorms and your wife works in the company canteen. And you get most of your paycheques deducted for that privilege, so going anywhere else is mostly theoretical anyway even if you had time off.

There's a great 99PI episode about something like this: Fordlandia (https://99percentinvisible.org/episode/fordlandia/)

Or, let your relationships fall apart because you are working essentially 100% of the time you are not sleeping eating and fulfilling the other basic responsibilities of life.

Extended family, yes. In China it's far more common for them to live together.

Everything is delivered in the big cities in China, so no worries there on the food / other services part.

China had only one day off a week for everyone as recently back as in 1999 when I first visited. The Chinese 996 system is common at Chinese internet companies, fortunately American companies operating in China are exempt from that.