I have created a few Elements and most of them hide the content title, e.g. “Full Width Pages” element, which is applied to all pages, but it makes no difference if I set it to entire page, still the title is diplayed.
your site is using a header element. Found in Appearance > Elements.
The one titled: Global Page Headers is whats displaying the title.
You can delete the header element or edit its display rules to exclude those pages.