It took me some time, but here's what I've done so far:
1) installed fresh Joomla 3.8.1,
2) installed SEBLOD 3.15.0,
3) installed Masonry template,
4) created very simple content type (consisting only of 4 already existing fields: title, alias, introtext and creation date) and made it an article object,
5) created Search Type for that simple content type and set Masonry the template,
6) created menu item for the search type,
7) created around 50 articles based on the simple content type, so I can check the load function.
Then I started testing. And no matter what I did, how many items I set in pagination, Joomla was always loading all the articles at once. I've tried Beez3 and Protostar built-in templates - no success.
So let's sum it up: whole new Joomla installation with SEBLOD only - and it still doesn't work. Please please try it yourself. I really have no idea what else I could do to make it work. It just doesn't.