Markus Kroetzsch, 08/01/2017 00:12:
The subclass of and instance of statements are actually used in very many WDQS queries, often with * expressions to navigate the hierarchy.
I think that's what Gerard meant: you don't have to know what's under the hood, as long as it works. When you get some unexpected result, you go check what went wrong in the chain of subclasses etc. This is at least what I do, although I also work with some more traditional people who want to know the full ontology before even entering their first statement (of course they get lost for a few months).
Nemo