External recruiters do that all of the time. I worked with the same recruiter when I was trying to get a job and when I was hiring through him. I knew he prepped candidates so I had to have a different set of interview questions and different coding interview tests (with an IDE on a computer).

I know of one company where the hiring manager had all of the candidates do a merge sort on the board. He used the same interview question for years. All of the recruiters knew what to prep their candidates for.