It appears that his UP inputs are a severe reaction to something about the a/c behaviour.
Lyman, this is a guess response based upon a few things.
1. Stated sensitivity of this model acft at high altitudes by people who have flown it, as compared to control sensitivity in the terminal area and altitudes.
2. Change in power setting
3. Pilots initial overcontrol of roll previous to the graph
The above considered, what HN's graph excerpt shows me is that as with roll, the PF doesn't have a good "feel" for his pitch control during seconds 50-85, so there's a bit of over controlling going on. Part of what he's doing looks to me like a response to a pitch change that you'd expect from an addition of power to TOGA, and in part to correct for his own various pitch inputs, corrections, and counter corrections that he apparently isn't happy with. Why unhappy? I think he's aming for a particular pitch attitude and not hitting nor holding it. (Could be wrong).
I am uncertain what pitch attitude he is trying to establish and hold.
From 90-100 seconds, he makes what appears to be a substantial counter correction in the nose down direction with very small counter corrections ... he's milking the stick a bit, trying to avoid overcorrection during that phase, and seems to be making progress in establishing his "feel".
Not sure where the CVR sync's up, but I suspect this particular correction is a response to PNF's warning about 'you are climbing' and 'go down'
Not sure what other forces you are referring to. Seconds 120 to the end, he appears to be deliberately walking the nose down. The graph ends in what appears to me to be the next set of corrections / counter corrections about to start ... though why the SS at - angle induces nose up at the tail end there confuses me ... seeing the whole timeline/graph would probably resolve that confusion.