FYI we (at Mecatran) do that kind of calendar "flattening" (we call it internally "calendar partitioning") for a few of our customers, for various reasons, mainly internal and technical.
For example, for Paris Metro lines, we reconstruct
frequencies from plain trips, but our internal algorithm requires calendars to be
This partitioning is rather simple, but it creates indeed new calendars and duplicate trips. Personally, I agree with you, I would not recommend doing that as a "best practice".