That trend has reversed since a very long time ago actually. As for RSX I'm not sure the ratio is what you think it is. For filtered texture accesses, the number of filtering and addressing units is the same, i.e. 24 pixels/clock for bilinear, 12 pixels/clock for trilinear or 2xAF with bilinear, etc... IIRC it's point sampling that can run faster.
G80 had faster texture filtering than texture addressing but that already got reduced in G92 and then they became genuinely the same rate (i.e. 1/2 rate trilinear) on GT200. It hasn't really changed for NVIDIA since then in terms of filtered texturing (unfiltered has varied a bit over time for both NVIDIA and AMD but iirc at the moment only AMD has a difference between the two: 32bpp point is full rate, 32bpp bilinear is full rate, 64bpp point is full rate, but 64bpp bilinear is 1/2 rate or at least was).
Was it a good idea at the time for e.g. G80? I'm not sure. It was nice in reviews to make 16xAF really cheap and really high quality compared to DX9 chips, I remember myself and others being excited about that at the time. But things have moved on and I'm not sure it matters as much, especially as there's more and more post-processing which will never use more than bilinear or point filtering. So for most of the frame you're not using trilinear or anisotropic and the extra filtering units would just be filtering hardware. There are probably other reasons I'm not thinking of why it doesn't make much sense nowadays, but hopefully this is enough to satisfy your curiosity...