Of course the RC isn't Errata, it's not a free poorly put together pdf hosting on the website under a product named after typo corrections attempting to correct statistic blocks and edited out for size content in already published books. The RC is a fully published and official supplement containing rule updates and sold off the shelves just like the Dungeon Master's Guide II, Eberron Campaign Setting, the Spell Compendium, and the Magic Item Compendium. Apples and oranges.
Indeed.
And I think perhaps it should be noted the extent to which most game companies REALLY hate the very concept of errata.
At first it was suggested that WotC wasn't even going to issue errata for 3E/3.5, much the way TSR virtually never issued errata for AD&D. Do some searching for that. It basically took them completely leaving out entire pages for TSR to actually post errata. Instead you got things like the "thoul" in BECMI.
What is a "thoul"?
A thoul is a creature that is part hobgoblin, part troll, and part ghoul.
Or, you know, it is a typo because someone's finger slipped up a row when typing "ghoul", but TSR doesn't make mistakes, so screw you peasants!
Aside:
Of course that was back in AOHell days, when getting errata off the internet was a chore. Then again, I remember when errata was something you had to send an SASE to the company to get, or, maybe, if it was really significant and the company was really customer friendly, they made available to FLGS to hand out to people. (Ah! The joy of the 10 page MegaTraveller errata pamphlet featuring critical charts completely left out of the rules books, and pages of line by line text corrections!)
Why do they hate errata so much?
Well, aside from their sheer arrogance and not wanting to admit they could ever do anything wrong, errata is a confession that they sold you a defective product.
And what do you do when you realize you have purchased a defective product?
Why, you demand a replacement of course! Or a refund if you cannot get a replacement.
Yeah, like that is ever going to happen!
These are game books, not cars, where you could die if something goes wrong.
Hardcopy game books that need to be completely reprinted to make corrections, not computer programs that can be patched by some code.
So no, they aren't going to replace or refund, so they aren't going to admit to any product defects, at least not in any significant way.
At first they tried to get away with some stealth errata via Sage Advice, but everyone hated that. So much that they converted it to a FAQ, which still tried to stealth errata everything, making everyone even more outraged.
Then of course they did 3.5 two years ahead of schedule because everything was so messed up.
Finally they gave in and issued limited pdfs that they never kept up to date or complete.
And be happy they gave you that much!
So indeed, the RC is NOT errata.
If anything, it is the "true" 3.75, with the SpC and MiC supporting it.
Put out minutes before the line was cancelled of course, and not actually labeled that way because it would be bad marketing. But that is what it is.
And no, it isn't the SRD.
The SRD with the OGL was always going to be a subset of the "complete" rules and product line. Seriously, be happy they actually updated the SRD with Swift and Immediate actions!