Lizzi Harvey, a tech writer at Google who works on a lot of the search related developer documents, said on Twitter that it normally takes about two weeks for the developer documents to be translated. So if the document is published in English on May 1st, it will take until about May 14th to be shown in other languages.
Lizzi posted this tidbit on Twitter when asked when a specific developer doc will be translated to French. She said "it takes about 2 weeks for translated docs to catch up."
It takes about 2 weeks for translated docs to catch up. Apologies for the delay!
— Lizzi Harvey (@LizziHarvey) January 23, 2020
So when you see a new developer document added or updated, give it a couple of weeks to see the translated version.
Forum discussion at Twitter.