We know the Google Indexing API should be used for just job postings and live-streaming content. If you use it for other content, it just won't do what you want. A Black Hat World thread seems to confirm that it doesn't work for other content types.
The SEOs in that thread are discussing whether it works and whether you should consider using it to submit content to Google Search. Most seem to say that if you do use it, the content is indexed and then within a couple of days the content is removed from the index.
Here are some quotes from the thread:
There is no point to use it. Posts gets deindexed after couple of days.
Same situation here. All site pages get indexed and after a couple of days the site: operator didn't show all indexed pages.
The reason for this is that the pages are likely not being indexed initially by the Indexing API but by normal Google crawling and indexing efforts. Google then deems the pages not high quality enough for them to be in the index and removes them. I doubt that the indexing API is helping or hurting here; it is just not working for indexing for content types it is not designed for.
Forum discussion at Black Hat World.
Note: This was pre-written and scheduled to be posted today, I am currently offline for Passover.
