Re: Please be patient and help my confused brain...
You are a little confused, I am afraid.
The 18-55 was, indeed, designed for the APS-C sensor, and gives a view through the lens of approx 29-88 in full frame terms.
The 24-70, although designed for full frame photography, gives a view through the lens of approx 38-112 in full frame terms on a camera with an APS-C sensor.
You cannot compare the 24mm end of the 24-70 with the 35mm setting on the 18-55, because you have to apply the crop factor (1.6x) to both lenses, irrespective of what format they were designed for. So, if you are looking through the lens with the 24-70 attached, set to 24mm, you will get a field of view equivalent to 38mm. Likewise, if you are looking through the lens with the 18-55 set to 24mm, you will get the same field of view. I hope this is clear, but if not, just try it - set your 24-70 wide open at 24mm then compare it with your 18-55 set at 24mm - the view should be (approx) the same.
You can't please everybody, so you have to please yourself