You're right, it is a two-way street. Candidates go in to the process hoping to get a job and employees go in to the process hoping to get a co-worker. Both are acting in good faith

Most companies disclose what their process is up front and you're free to opt out at any time. Intentionally wasting the time of the recruiters and engineers at companies you don't want to work for just to "practice" just seems really rude