It's been there since March 1st 2020: https://github.com/privacytools/privacytools.io/pull/1672/files#diff-338290deae83c3bc8c6392188f6d96b5
It also says, which I am sure you will disagree with:
> Rather than use email for prolonged conversations, consider using a medium that does support Forward secrecy.
And guess what? That's not email.