Related queries return only editorial entries using REST API

We're running Commerce 9.6 site with Find version 10.0.0.3291 and we're facing an issue with Related queries described in this post from 2014: https://world.episerver.com/Modules/Forum/Pages/Thread.aspx?id=91180

When we're trying to use the REST API for related queries described here:
https://world.episerver.com/documentation/Items/Developers-Guide/EPiServer-Find/10/search-statistics/introduction-to-search-statistics/

we only get hits for editorial content, as in manually added suggestions. Our statistics tracking is on and I can see these kinds of reports from the Find UI:

But when I do a query to https://ourdomain/find_v2/_didyoumean?query=vaihteistonostin&size=1 I get this as a result:

{
   "status":"ok",
   "hits":[
      {
         "suggestion":"nostin",
         "type":"editorial"
      }
   ]
}

So for some reason, the automatic "vaihteisto" suggestion is not returned as a related query. Is there a missing configuration or something similar that's preventing the dynamic suggestions from getting returned?