Unfortunately my own theory about why the SD is crippled is more annoying. Because SD can be cheaper and nearly as fast as CF, which would move the 5D3 closer to the 1dx than canon marketing wants.
No proof, but certainly reaonable based on other behavior.
Wait, wait... You seem to be suggesting that Canon would intentionally cripple a camera model?!?
The 5DIII and the 1D4 share the same unit. Personally I only have the SD for overflow should the CF fill up. I soon realise that I have switched. On the 1DS3 at 5fps it is not such a problem as the SD speed doesn't slow it down so much
Why do people think that Canon cripple a model rather than not give it all the bells and whistles? I suspect in this case they have filtered down the unit from the 1D4. If it was good enough for the 1D4 users it should be good enough for 5DIII users. More a case of looking for minor improvements that could have been incorporated and turning them into a major issue
Just remember the 5DIII arrangement is better than the D800
You know...that actually makes sense they would take the card unit from the 1D4. Tried, tested, already have the tooling for it. Makes sense I suppose. Unfortunate that they didn't update it to UHS-I.