Just about every VHS featuring the song spells it as "Do Op Hop" in the song listings on the back of the releases, though I'm sure it's spelled "Do Wop Hop" in the MTV-style credits in Count it Higher. I don't know if the chapter stops match the song listings.
A lot of song/sketch titles tend to vary depending on sources (CTW Archives documents, sesamestreet.org, hulu, Sesame Street youtube channel, DVD chapter stops, etc.). It seems like the pinball cartoons are called "Pinball Animation" just as often as they're called "Pinball Number Count" (and according to Muppet Wiki the song was originally just called "Number Count"). I didn't notice until just recently that on Old School Volume 2 that the #4 cartoon is listed as "Pinball Animation #4" in the chapter stops (or is it the booklet?), but is listed as "Pinball Number Count #4" in the booklet (or is it the chapter stops?).
Another title inconsistiency: The news segments have a title card reading "Newsflash", while Kermit, the announcer, and others always refer to it on-screen as "Sesame Street News", and yet the Old School and 40th anniversary DVDs list them as "Kermit News" (which doesn't make sense as a title, aside form the fact that Kermit is the main reporter). Sesamestreet.org uses both "Kermit News" and just "News" in various titles (but never uses "Sesame Street News" as a title). I know that "Kermit News Theme" is the registered title for the theme music. And Hulu lists the sketches as "Muppet News Flash". I can't remember how Sesame Workshop lists them on Youtube.