Any lesser part at all, much less something as important as a GPU, immediately limits developers from fully taking advantage of the more-powerful system's hardware.
I mean, technically, developers can still put 100% into the more-powerful system; but, realistically, that won't happen. Developing for two systems is inherently more demanding (and costly) than for just one system. This is on top of already trying to make multi-platform games, which already requires time, effort, and money from developers.
That's the problem with the Series S. It limits budgets, which, in turn, limits games.
The "best effort profile" requires time which could be spent elsewhere if the Series S didn't exist. That's why it's inherently detracting from the overall game-quality.