I don't want to speak for others but that is exactly the way I experience it. I can sink deep into an unimportant but complex analytical problem after lunch and the next time I take note of time passing, it's 3AM and I forgot to drink, eat, go home, exercise, love, and sleep.

The amount of focus I'm capable of is not the problem. The problem is putting it to use where I want to, rather than where it, by pure chance, happens to end up for the day.

It also applies to the small stuff. Someone asks me to bake a cake and I think it's probably best if I know what temperature it should bake at. An hour later they ask me how the cake is coming along and I realise I know a lot about the chemistry of baking but I haven't brought out the flour yet, and I no longer have time to shower, shave, send that important email, and clean up after baking.

I go back and forth between viewing it as an inability to perceive time and an affliction of directing behaviour. Perhaps they're two lenses through which to view the same thing, and I haven't yet discovered their symmetries. (Only vaguely aware of them -- directing behaviour to achieve future goals requires the ability to perceive time acutely.)