While I concur that it's a bit misleading nothing is stopping you from using your own key and mail client (albeit with their "bridge" solution) to send E2EE e-mails.
If you rely on the keys they generate you can export them and use them accordingly but one should be weary of the handling of said keys if they were compelled to make a backdoor as others have noted.
That being said this does leave a bad taste in my mouth.
While I concur that it's a bit misleading nothing is stopping you from using your own key and mail client (albeit with their "bridge" solution) to send E2EE e-mails.
If you rely on the keys they generate you can export them and use them accordingly but one should be weary of the handling of said keys if they were compelled to make a backdoor as others have noted.
That being said this does leave a bad taste in my mouth.