The Seduction output impedance is fairly high - 4K or 5K approximately. Cable capacitance will require extra current from the output stage at high frequencies, so the short cable is intended to minimize that extra current. Incidentally, the output stage and its limitation are the same in the Eros.
There is a substantial margin built into that requirement; the measured frequency response and power response won't be affected until the cable gets pretty long, 5 to 10 meters I would guess. But most careful listeners find some subjective loss of treble cleanliness and detail long before the simplistic measurements show an audible frequency response loss.
I've designed two RIAA preamps with greater drive capability, both needed an extra stage to do it. One had a cathode follower, the other a line driver with output transformer. It can be done if you need it, but it can't be done without at least a little sonic price to pay.