The precompilation tool does not compile Feather templates, as well as, custom layout controls. This means that the compiler will run the first time a template should compiled. Furthermore, the csc.exe could run in several occasions even after the precompilation. It could fire for code in the global application class (global.asax) or in the App_Code folder. It will be executed also if you are using many custom MVC widgets.
However, you can perform a test using default controls (for instance, content blocks) and the compiler would not be fired after the precompilation. You can give it a try with duplicating pages with same widgets and calling them in a row.
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