^^ yep, did those tests too on my J30 before and after installing a grounding kit, couldn't notice any difference on the signals from the CAS, AFM (MAF), Speed sensor, TPS, or on the Transmission Revolution sensor. But my factory grounds were clean and in good shape.
Although I used a Fluke Scopemeter.. haven't seen a working CRO in a few years now. (unless you are using the term generically.. not really meaning Cathode Ray..).
I guess Nissan could have gone backwards with their wiring quality over the last 15+ years.. but as vimana said, sensors don't need anything near the size of grounds compared to those requried by high current devices like starters, AC compressor clutches and ignition coils, and they all seem to work ok.