A mis-representation that folks often have is that a proper caulking job has to be a thick, unsightly, 3/4" smeared bead to do the job. That isn't true. A nice, fine, tidy, professional bead is all that it takes to keep water from entering, and if applied properly it is fine to caulk over the grout joint as long as the grout joint is just as tidy. If I have the time to grout first and let it dry good, I prefer to caulk over the grout, as it acts as a "backer" so that the caulk doesn't suck into the jointleaving it uneven looking, and the chance of pinholes.
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Don't make your work wrong to make someone elses right.