bill good said:
There has never been any sense in keeping voltage across a Li-Ion battery when 100% SOC. It is like trying to overfill a fuel tank. But this is only one hole in the swiss cheese model.
Not the same Li chemistry, but I believe that at least some plug-in EV manufacturers recommend that for maximum life their battery should not be left idle for long periods with an SOC above 80%. They advise to top off the charge shortly before using it if full range is needed.
Since under expected usage, the 787 batteries will be sitting without loads almost all of their lives, this could be an issue.