That's only one of many problems with converting office building to residential. While a few conversions have succeeded, usually it's cheaper to just demolish the building and start from scratch. Allowing windowless bedrooms won't change that.
I've no idea about Japan or China, but I do know that "office-to-resi" has become reasonably common in the UK.
Since 2013, it's been classed as "permitted development" (so, automatically allowed as long as the building isn't listed as architecturally or historically important), and liberalised further in the early 2020s.
House prices have outstripped commercial rents for most of this century, and change of use is cheaper than demolish-and-rebuild, so I'd expect to see the trend continue.
The issue with unsuitable floor plates is real, though, particularly in larger buildings. One solution is to cut chunks out of the curtain wall, turning part of each floor into an open-air terrace which functions as a light well. The reduction in useable floor area means that's only really viable at the premium end of the market, though - a prominent (albeit mixed-use) example is https://www.constructionenquirer.com/2024/07/18/striking-new...
The problem is you can't easily convert office buildings to housing without these, because the floor plates are too different.