Oh, there they are. Btw, the header link, https://itch.io/game-development is empty ("see all tools", on directory)
I had to think what auto completer meant. Yes, the results while typing do show the special tags and platforms. And the actual results will not.
I thought it might be a simple matter to just include the special tags in the list of the suggested tags, so they would also appear as search results and also be visible when using the suggested tag box. That one does not have an auto completer. It only searches the content of the drop down box.