I don't think it means anything. It's just a coincidence with how we view power levels. AT certainly wasn't thinking "ah, yes, there should be a 25% gap between these two in order for Vegeta to be able to do this to Kui." Vegeta and #18 should be a larger gap in order to fit Cell and suppressed Piccolo in, although I guess Piccolo can go between #18 and #17 and the statement would still work.