[garaetjjte]

>Official Mono releases have switched to do that since then, but (I think) for backwards compatibility reasons Unity never enabled that functionality and kept everything at double precision so far.

Probably because Unity uses ancient Mono fork. And that apparently started because they didn't renew their non-copyleft license with Xamarin.

[aras_p]

That is not actually true.

Unity used to be on ancient version of Mono before year 2017. Then until 2019 the option to use “up to date” version was optional. Since 2019 it has been on more or less current Mono version (Mono itself stopped getting any serious updates around 2020).