TLS feature missing

[Tributh]

Hi,
i was using dovecot 2.2.25 compiled with opnessl 1.0.2
I realised with a cipherscan utility that i was able to support
mulitiple TLS curves.
Now i upgraded to 2.2.27 with opnessl1.1.0 and was falling back to
historical stages where my server only servers one TLS-curve: secp384r1
right now.
One big reason to compile the new ersion with openssl1.1.0
was to bring CHACHA20-POLY1305 ciphers and X25519 curves to modern clients.

The ciphers i am estimating are working fine, but X25519 and also
secp521r1 ist now longer supported, like it was in dovecot 2.2.25.

Is there something broken?
Or a new (know missing) config feature?
Or is it a bug ?

Regards Torsten