Agreed. But the metric is interesting regardless of the lying because it seems that many voters don’t care whether Trump lies, they only mind he doesn’t lie to them. The fact his promises are based in falsehoods is secondary in the minds of those who want him to fulfil his promises.
So yes, I would say that Biden is the more morally upright of the two, but is that the factor which will see him elected at voting time? Trump lies, but he didn’t lie to his core voters about what he said he would do.
Ultimately what will see either man elected is their appeal to the disaffected middle and floating voter. Both men are weak here and could be usurped from within their own party (and likely will be) but Trumps lying isn’t a negative factor for his core voters…. And given the limited move to the democrats in 2020, I’m not sure it’s much of a problem for some of the middle voters either.