Vortex Sound Research

So I'm aware of the normalled routing of each oscillator to its opposite osc's FM input with the attenuator right beside it. I read in the part of the manual that explains the internal routing options that one of the options is routing to the FM:

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https://preview.redd.it/rgdjg6r8mgua1.png?width=525&format=png&auto=webp&s=15febdb10b73b5a291f873e44580b77f16ce66fd

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Unless I'm missing something here, wouldn't that be redundant? is it just about coupling that FM connection to the main Index knob to control it simultaneously with the other active internal modulations?

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Thanks in advance