I think the difference is that SM was expected to be down that long. IIRC it was always publicized as a 2+ year project. I'll admit that I don't know for sure if it reopened on schedule or not, but it seems to me it did. With BMTRR the reopening date just seems to keep being pushed out further and further. That's the part that's kind of frustrating. The fact that we get our hopes up instead of regarding reopening dates with a healthy dose of skepticism is our own problem, I guess. Of course, 'stuff' happens and Disney's gotta do what they've gotta do to see that BMTRR is up to standards (artistic, mechanical, & safety).
'Officially', BMTRR is still scheduled to reopen 2/1 according to the Disneyland website links. Frankly, I'm wondering if the reason the POTC refurb that is/was 1/27 - 2/13 appears to have been delayed is because BMTRR won't reopen on schedule and they don't want to have Splash, BMTRR, and POTC all down at the same time. It would sure make that side of the park seem dead with three 'anchor' rides down at the same time.