I'm really out of the game these days so don't know the state of different options, but to be fair, a decade ago I had a team member try and cheap out on modules and it caused a fairly decent mess. Lots of failures, but not just outright failures, but problems where the link would mostly work, but through a bunch of fiber taps and bypass modules produced a high error rates when installed.

So I'm not saying it's right, but I can at least understand where a mandate like that might come from, if perhaps outdated compared to the current state of the industry.