Well, I think the idea above wasn't that you shift your schedule (relative to the Sun) but that you keep it and get used to that your work day starts at what us

Well, I think the idea above wasn't that you shift your schedule (relative to the Sun) but that you keep it and get used to that your work day starts at what used to be 9AM but now the clock says it's 9PM. And it would be 9PM at the same time in Beijing, and in London but you'd have to know that 9PM means evening in Beijing and early afternoon in London. Which is a lot harder and a lot more to remember than simply knowing the TZ difference to these two cities. (Because you'd have to remember when the morning starts, when it ends, when afternoon starts, ends, etc. for each timezone.)