This is the same way Intel used the i740 as a tool to promote AGP. The i740 drivers (and perhaps the hardware) were incapable of mapping textures from local memory. Since all textures had to be stored in system memory, the marketing diagrams showed "OMG! AGP2x is 4 times faster than PCI!!!".
The i740 architecture eventually became integrated into the motherboard chipset as the i810. In-memory texturing makes a lot more sense there.