So what? RAM is RAM, no matter if on-chip or off-chip. The comparison with cache is not applicable, cache isn't RAM, not even remotely.
Not necessarily...the RAM on the A4 is directly attached which means that it has a shorter (quicker) access path to the CPU. RAM is connected to the processor using ARM's 64-bit-wide ABMA 3 AXI bus. So given the choice between off-chip and on-chip, for a device that is not upgradable, the choice is obvious from both a performance and packaging perspective.