Ah, that's right... Jocko.
In fact I think it was mostly him doing the 'Buster' stunts like these, not Jo.
For reasons like this, I sometimes call the series: The high-flying misadventures of Jocko the chimp, featuring his little accomplices Jo & Zette.
Good question!
There's a lot to unpack across these two links: [short films] and [feature films], but skimming through quickly, it seems like there's two main points:
In terms of running length, it seems that the total number of 35mm reels (2-4 I think?) and total film length (35 - 40min it seems) tended to suggest a "short," while longer films could be said to be "feature-length."
A completely different definition for "feature film" was based on it being the advertised lead film on the marquee. So I guess it's possible that a film could be both a short and a feature film at the same time(!) Note: in that era, no matter how long the feature-film ran, I believe it was typically accompanied by a short, including cartoons and newsreels.
Anyone feel free to take a deeper dive and correct any of that, please!
Btw-- what films were you thinking of...?