"Tightly integrated" can mean "We designed A and B to fit together well. We built them side by side and tested them together" That's perfectly acceptable and can make a fair direct case to the customer.
What's not:
* Not allowing controls to manage integrations. Maybe I want to connect A to C, D, or Q instead, or not allow a connection at all.
* Accidentally-on-purpose clobbering customer choices (ooh, whoops, we reset all your file associations for the sixth time this year, perhaps now you'll stop changing them).
* Using undocumented APIs or similar gimmicks to ensure a competitive product will be inherently hamstrung.
* Pretending a seperate product is an indivisible component of the whole. I'm sure there are a bunch of places where Edge could be pulled out in favour of an external help-file/PDF/etc viewer.