Again, not to start pointing fingers, but its all hearsay.
Technically speaking, I doubt that. Voltage = pump RPM. Amperage = tq the little pump makes more or less.
Voltage shouldn’t change much at all wire thickness wise, but amperage can. Thinner wire = less amperage HANDLING over time. If the gauge of the wire meets the spec for the pump, it can be speaker wire, trailer wire, household wire, or what ever, and it wont make a lick of “performance” difference.
IF the wire was too thin, and the heat built up, the amperage could drop which as the pump is under load MIGHT not make as much power as it should have and flow less… but thats a LONG shot in my head.
kk disclaimer… Wasnt there, didnt see the car, done know the pump, the wiring spec, the wiring type, dont have my electrical properties hand book out to verify my theory. :rofl