No, GS does not use OAI-PMH for fetching articles.It is their GoogleBot (either the standard or the mobile web bot) that fetches the web pages, and depending on the meta tags in them, pages are being classified to be indexed in Google Scholar or not. OJS enables the Highwire Press tags if the Google Scholar plugin is enabled.
If you want that or pages are indexed faster by Google and Google Scholar, you may do the following:
- register for a Google Webmaster Console account
- enable the GS plugin in OJS
- submit your journal site(s) and the corresponding sitemap(s) there
See also Google Scholar Indexing for further help.