The Jia Tan xz backdoor attack did get flagged by some automated analysis tools -- they had to get the analysis tools modified so that it would pass -- and that was a pretty sophisticated attack. The people running the testing didn't catch it, trusted the Jia Tan group that it was a false positive that needed to be fixed, but it was still putting up warning lights.

More sophisticated attackers will probably replicate their own code analysis environments mirroring those they know of online, make a checklist of running what code analysis tools they can run against locally prior to making the code visible, tweak it until it passes -- but I think that it definitely raises the bar.

Could have some analysis tools that aren't made public but run against important public code repositories specifically to try to make this more difficult.