Good points.
I did a little digging last night after my post above yours.
I went to forums for other fitness bands/smart watches and guess what? They all have endless posts about inaccuracies of their respective pedometer apps. Some record too many steps, others, not enough.
Interestingly, early posts on a couple of different Fit 2 forums show owners complaining of far too many steps recorded.
So, apparently, there's no silver bullet here.
For me, I don't care if a few dozen steps don't get recorded when I putter around the kitchen for a few minutes. What I want to know is did I get over 10k steps in a given day? Even a few hundred plus/minus really don't matter to me. Further, since I will not be switching out between different fitness bands on a daily basis, as long as the Fit 2 is roughly consistent with itself, things like trends will be reasonable accurate.
I'd extend this same thinking to the stair counter. Plus/minus some is not really a deal breaker for me.