The article says the exact same things - you're just rephrasing it. The point it makes is that it's okay to work on several projects, the important thing is to finish at micro level.
This nails it. The article isn't entirely wrong but focus isn't a myth. Our eyes can't focus on two things at the same time. We too can't give full attention to multiple issues at the same time.
Working on multiple projects makes you feel like you don't have time to waste, and so there is a tendency to make better use of time worked on each. There is also a need to properly prioritize across projects - which might be a considered a way of sneaking "focus" back into the picture after all.