I recently upgraded one leg of a revenue WTP flight I have down the line using Avois into CW, and I started to wonder, in the rare chance I get offered an AUP into F what would happen with tier points if I accepted. As of now that flight now shows a booking code of U, so my assumption is no TP bonus.

Although then I saw in the AUP sticky thread, this statement:
"AUPs do give additional Tier Points and Avios, so long as the underlying ticket is a revenue ticket. That includes revenue tickets where Avios were use to part pay."

I am pretty sure this is referring to the price reduction capability of Avios, but does it also cover an avios class upgrade?

In the distant past I did a book + upgrade combo once (W to J) and IIRC the way that worked was I actually got WTP points. Although that was done at the same time.

Thanks for indulging my curiosity