I work from my bed, I work at my desk, I work pretty much everywhere in my home and it's not at all a problem. I'm really annoyed by these overgeneralisations about what's right or wrong for individuals, and all these buzzwords about "separation of life and work", "work-life balance", I love my work and I sleep like a mule even if I work ten minutes before I go to sleep.
I don't at all get these neurotic optimisations that people make, and having random strangers tell them how to live in their own home. If you like to work from your bed work from your bed, if it doesn't work for you stop, but to tell people they're delusional is nuts.
It's not just about this particular topic, there seems to be an entire emerging industry of life-coaches, sleep and whatever else coaches who try to convince people of strange norms that they have to uphold in their workplace or home. It's like the Western version of Feng Shui or something, oh no you slept badly a week, bring in the sleep coach to rearrange your furniture and exorcise the bad software from your bedroom
I'd suggest people who need to compartmentalise their work from their life this much to ask if it isn't that they're unsatisfied with their job that makes them sleepless rather than doing work on a bed.