GANZANSENPU*..!!

They wanted him to still say "Ganzansenpu", but have a little text box explaining to those unfamiliar with Japanese that he isn't just screaming in gibberish. Most anime do it like that, but usually without the translator's note, just expecting readers to understand that "Kamehameha" is the name of the attack, and roll with it, as opposed to having Goku shout, "Turtle Destruction Wave."

I guess it's worth noting that most of the other attacks in DBZ are actually translated into English for some reason, but Kamehameha was left alone. Is it weird that Krillin says "Destructo Disc", but Goku's signature move is still in Japanese? A little. Maybe that was a stipulation set by the licencors. Stuff like that happens. It's not a constant across all English translators, nor is it consistent within individual series sometimes. Even in Berserk.

For a more contemporary comparison. My Hero Academia introduced a character named Geten. Fan translators got to the chapter before Viz, and translated his name as Apocrypha, the literal translation of the word, but Viz kept it as Geten, because there's no reason to translate a proper noun.

It's completely different from "keikaku means plan" because it should have just been translated as "plan". It's not a special word or term that could warrant being left alone, such as the name of something.