Google showing H1 text instead of page TITLE in search result?

Question

I always thought Google shows page title (whatever is in the <title> tag of the page) as 1st line of each result.

But looking at the search "orologi da collezione" below, it seems Google is showing as 1st line of content the <H1> tag.

Am I right? Is Google showing the content of the H1 tag as 1st line of the serach result or something else got from meta description?

Even more and more interesting when searching for "vendita orologi" the same site comes out, but this time it shows the real page title as 1st line:

Answer 1

Page title

If we’ve detected that a particular result has one of the above issues with its title, we may try to generate an improved title from anchors, on-page text, or other sources. However, sometimes even pages with well-formulated, concise, descriptive titles will end up with different titles in our search results to better indicate their relevance to the query. There’s a simple reason for this: the title tag as specified by a webmaster is limited to being static, fixed regardless of the query. Once we know the user’s query, we can often find alternative text from a page that better explains why that result is relevant. Using this alternative text as a title helps the user, and it also can help your site. Users are scanning for their query terms or other signs of relevance in the results, and a title that is tailored for the query can increase the chances that they will click through.

If you’re seeing your pages appear in the search results with modified titles, check whether your titles have one of the problems described above. If not, consider whether the alternate title is a better fit for the query.

Read the rest here https://support.google.com/webmasters/answer/35624