As a alternative to the classic MDI, using a tabbed based interface is actually better.
As I - and some others - explained this is not always the case. Not only when backporting.
Tabbed based interfaces have their own drawbacks, specifically visibility. That's a very BAD thing.
What MS intended is to switch over to a document centered abstraction, which does not mean tabs.
It means the document is presented at all times and the tools to workwith the document are displayed on demand, depending on context.
They call that SDI. And doesn't exclude that one of the tools is another copy of the document visible at the same time.