I have no clue either nor did i go back to check upon hearing that remark, maybe they just want it that way, he is a rather unimportant character to the series as a whole, to Wa-san he's some what of significance but nothing that's big,(if anything the episode that mentions there past just help build Wa-san character) and further in the manga I've yet to see him to anything, so let him shrink, won't really ruin my fun watching each episode