However, that doesn't mean it wouldn't have made sense for Goku to attempt the Kaio-Ken. For all fans know, a full-power Kamehameha with a multiplier could have had a similar effect on Buu as the ...

Goku uses Kaio-Ken x3 and then a Kaio-Ken Kamehameha, which Dr. Wheelo confidently counters. Goku escalates the encounter with Kaio-Ken x4, which sends Dr. Wheelo careening into outer space.