The trouble with the pun is that it depends on being
1) written
2) in romaji
3) in a very literal (waapuro-roumaji) transliteration.
It's very common among Western anime fans to still prefer the style of romanization that would let you represent each kana in the pronunciation of a Japanese word with a direct set of ASCII characters. In Japan itself, this style is "waapuro-roumaji", where "waapuro" is short for "word processor". My understanding is that any of the recognized official romanization systems wouldn't preserve the う in おう as a distinct 'u'. Even the old Nihon-shiki scheme, which otherwise preserves a non-phonetic direct kana-to-latin-letter(s) transcription, uses 'ô' for a long 'o' sound.
My personal theory is that back in the day, this let certain fans lord it over other fans on USENET, which could only use ASCII. "No, his name is Soun Tendou! Get it right!"