1 It's more like the SD card speed is pathetic.

2

Sigh.  Sadly, he's probably right for most users.  Having said that, VMS could join directories two decades ago, and Windows has done it for years ("libraries" in Explorer) so it's not as if you couldn't, say, combine a Pictured directory on the tablet with one on a card.

Where I think you come into more problems is with multiple apps not being standardized to storage locations.  I rooted my phone last year, and tried probably a dozen different roms, and a bunch of camera apps, and do you think any of the third-party apps would use the standard directory, or even the same directory as any other app?  No, and now I have camera images scattered across half a dozen locations.  People like to bash My Documents in Windows, but this is why Microsoft invented it.

3 SD cards can be slow - particularly the cheap ones - but that's not the excuse he used.  Instead, he said that it's too confusing for users.

Isn't it rather his job to fix that, rather than to rip out functionality?