First, I would not trust the engine in a position where not that much is happening. It has no clue what it's talking about. If you are going to trust it anyway, at least try to see what the answer to your "inaccurate move" is suggested to be.
But I think it's kind of right in this case: 3.c4 appears to fight for the center, but I'd say it makes your fight for the center more difficult. Compare for instance 3.Nf3 d5?! 4. e5! with the lines given by Annatar, where it's not a good idea for White to play e5.
White could here take a chance to develop its pieces, probably with 3.Nf3. If ...b5 is no threat, 3.Nc3 would also be OK. 3.Be3 and 3.Bd3 are fine but a bit more "committing". Flexibility is probably another reason against 3.c4 (you won't be able to take the pawn backwards, so your queenside will remain a bit weaker)
If you check your King's Indian example, most engines will probably suggest 2.Nf3 (or even 2.Nc3!?) rather than 2.c4 unless they are using an opening book (engines have had a "pro-development-bias" for decades). I'd like to add that the situation is indeed quite different as the oppponent's dark-squared bishop will not go to b4, for instance, as in the lines by Annatar, so one of the main inconvenientes of playing c4 is not anymore.
As a final remark on general opening principles (which only partially applies to this case), please try to differenciate between central control and an overextended center. Just because we have a lot of pawns in it, it doesn't mean we are winning the fight for the center. You may want to have a look at some Black victories in the Grünfeld's main-line or the Four pawns attack for some illustrative games