Actually, those notices are general notices and they may or may not give you the full picture.
Some of them are harmless, and some may not be used to infringe users privacy but are needed for the add-on to work.
There are also some add-ons that do things that they shouldn’t.
Unfortunately, without inspecting the add-on code, it is not possible to see what they actually do.
It was also discussed in Understanding Extension Permission Requests .