Google is testing not just large titles for grouped snippets but also large titles that are fully bolded for Google Ad results.
Here is a screen shot from Andrew Rodgers who shared this with me on Twitter:
Google is not bolding the title because it matches anything in the search query box. It is just bolding the title because it is testing a new look, I suspect.
I do not like bold things... :)
Forum discussion at Twitter.
It is not just ads I am told:
Not specific to Ads. Just the very top results. So applies to organic if there is not an ad there.
— //Andrew Rodgers ☘ (@AndyNRodgers) July 10, 2020
Update in 2022: More bolding font tests:
Google is testing bolded font for me again on some browsers. #noOnecares pic.twitter.com/FD1CaIJSpQ
— Mordy Oberstein 🇺🇦 (@MordyOberstein) August 18, 2022