smcl parent
Shader compilation is well known though, and anyone halfway serious about benchmarking these things (like Digital Foundry) factor this in and control for it
Yes, and anyone halfway serious including DF usually don't find Denuvo having any noticeable effect on performance
DF's claims isn't that it doesn't have any noticeable effect in performance (in fact in a recent video[0] they claim the opposite when Denuvo was introduced to Assassin's Creed Mirage after reviews were done - it can affect performance and thus because of that introducing it after the fact invalidated the CPU performance metrics reviewers had done) but - at least in the cases i remember - they cannot tell if the issues were due to Denuvo or not.
Note though that in a case where they could test both versions, they did find Denuvo to both have lesser performance and affect frame pacing[1] (though that is for a 2yo game, things might be better more recently).