I think that Li Plating and "dendrites" are something they have been looking for from day 1. Dendrites also is not a very specific term.
There's different types that have different impacts on the batteries performance.
You can find an interesting article about the topic here:
Whiskers, surface growth and dendrites in lithium batteries
Disclaimer: while being a physicist with interest in li-ion technology, I'm far from an expert.
Usually a single small short in a battery won't cause the battery to fail. The short circuit will melt itself and disconnect. You're only really in trouble if short becomes big enough to reach thermal runaway. Lithium plating, fingers, dendrite - this all should at first only affect very small parts of the large surface area of a li-ion battery. As the issue accumulates over time, problems get worse though.
The plating happens at a *cell* voltage of 4.2V or higher. So when you're charging either to a high SoC or with a lot of power, your charging voltage ideally would be exactly 4.2V once you reach a high enough SoC not to overcurrent the battery, since current = voltage differential * resistance. -> The higher the differential, the higher the charge current.
The trouble is, you don't charge every cell on it's own but a module with many cells in serial and you want to keep every cell below 4.2V. The voltages are distributed according to the internal resistance of the cells (see voltage divider), which again is also dependent on the amount of plating and other internal cell factors and even slightly varies across the surface of the cell. Even more it can change while you're charging if the lithium ions cannot intercalate into the electrode fast enough.
Long story short: my only slightly educated guess would be that they were looking to mitigate a certain failure mode related to Li fingers (X) and found something completely different (Z), maybe some previously unknown interaction between the electrolyte and the electrodes. It might be something really minor that is no big deal but might extend the life of the cell if handled properly.
These issues are usually really really complex and deeply researched though, so I don't think chances are high that some random guy on a forum with zero to no information guesses even close to correct.
If you wanna keep your battery free of metallic lithium, I guess it's a good idea to always keep the charging voltage a good bit below the maximum. For my (unaffected) P85D my latest data shows: if I want to stay below 4.1V / cell (~394V total, which should hopefully be plenty), I should stop charging at 75% with 32kW or slightly above when charging on 22kW.
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