Oh, now I get it!
On Spain's Amazon Prime Video there are 3 versions of King Kong (1933) with different lenghts. Only 2 of them are avalible with the basic suscription and the other one is on a channel. I was so confused since I tought that maybe the difference was on the end credits and maybe one had the dub actors listed and the other not or had the distribution company listed or something like that. But then I tested and the end credits already start at diferent points and the opening credits are the same, so I was confused about the diference between the two cuts. Now I realice that the version that I saw had already the Lost Spider Pit Sequence inserted. From that mess of version I got the 30 chapters listed in the timeline for King Kong (1933). I was planning of buying it in DVD at some point to see if the chapter titles are more "normal" there.