if u know how to hold ur pedal when running dyno, it shud be able to tune all rpm range.. at any cell...
that's the thing, with honda ECU, TPS is also a factor in tuning, that's why simply whacking half throttle don't work, because at below 80% TPS, the ECU applies correction, and that is why you can't get repeatable AFR readings. If you whack 100% throttle, you can repeat the AFR readout, but you won't get it to reach certain cells.
On the road, to get those cells also sometimes quite difficult on full throttle. usually have to find an uphill to test.
Also, IAT/ECT temp vs. ignition compensation is also more realistic on the road. Actually I do wonder why some japanese tuners insist on running the cars they tune on the road, so I asked one, and he said (and my japanese understanding is horrible, so not 100%) something about on road condition is not same with dyno.
Thinking about it, it's true in a way, because the blower fan cannot replicate real life situations. I do notice sometimes there are lean spikes on some cars that got tuned on the dyno. They're not necessarily critical, but it shows that dyno's do miss things.
There's also variable load dyno that can address the above shortcomings, but in the end, the dyno room is still an 'artificial' environment.