The difference here is assumptions being made. Me, like most people, assume BC means you open wth box and put in your old games and they run. PS2 was advertised as BC and that's what it did. The GBA was advertised as BC with GB and that's what it did. The Master System adapter for Genesis was advertised as allowing you to run your Master System games on Genesis and that's what it did. None said 'No updates, patches or recompiled executables required'. It was assumed that none of these things were needed.
MS talked of BC for XB360. At first they said it wasn't a priority. They then announced BC was to feature (woohoo!). They then explained that it was a 'partial' solution, in that it was specifically targetted for 'the most popular titles' and would need a level of recompilation for some titles to work. That's the first time I've heard of BC having a more in-depth explanation of what titles it supports. I tell a lie. The Amiga A1200 had backwards compatibility with older Amiga software but Commodore advertised that not every game would work because of issues with the software.
Now if Sony have, as you suggest, got a partial solution that needs XB360/A1200 like patches and fixes, why are they not saying so? Are they really going to risk the PR nightmare of advertising BC for 13,000 games and then when we put our games in half of them don't work, just pass that off a BC anyway as though they didn't need to explain this was a limitation of their solution?
People's expectations in the main are that, unless stated otherwise, a BC solution means out-of-the-box, play your old software. If there are any variations to this, if a noticeable number of titles aren't BC out of the box compatible, we expect to be forewarned. You obviously have a different take. Perhaps when Nintendo announced you could play GB games on your GBA you thought to yourself "Hmmm, maybe, but will that be all titles? Will I need to purchase new compatible versions, or get a flash card which I can upload new executables onto?". Perhaps when Sony announced PS2 would play PS1 games you thought "yeah, but will I need to buy a HDD to download patches onto so I can manage this? Will I need to buy a disk of patches to run before loading the game proper like Amiga had to?"
Just a different take on the matter I guess, but I don't see reason to be that skeptical of Sony's current announcements on BC. I had no idea at the time how PS2 was BC with PS1 but it was and worked, just as Sony said it would.