Can also be seen as a gentle ribbing of the more....paranoid, aspects of the Toonami fanbase.
It's a coincidence, because the content warnings air hourly, but there was a time during which they aired immediately before Sym-Bionic Titan and ThunderCats—two shows that aired on Cartoon Network (albeit with TV-PG ratings instead of the standard TV-Y7-FV ratings) and didn't contain anything to warrant a TV-14 rating or higher.
On a related note, most of the IGPX episodes that have aired since the first one so far are rated TV-Y7-FV (with the exception of one episode that aired with a TV-PG rating). It's especially amusing when you consider that the 2013 promo for IGPX advertised the show as being rated TV-14-DSV.
TOM apologizing about airing the pilot and Episode 2 of Thundercats out of order by mistake during its planned rerun. "Sometimes I really AM just pushing buttons." And then goes on to subtly reference Dexters Laboratory, another Cartoon Network original cartoon, with "what does this button do?"
On the One Piecepage on adultswim.com, [adult swim] added the intro used for the 4Kids dub. A token of nostalgia for the people who enjoyed the 4Kids dub, or [adult swim] just being their usual selves? You decide.