[TLS] RFC8446 backward compatibility question

[Toerless Eckert <[e-mail]>]

I am trying to figure out if every implementation compliant with
RFC8446 is also necessarily interoperable with an RFC5246 peer, or if this
is just a likely common, but still completely optional implementation choice.

I could not find any explicit statement that backward compatibility
with RFC5246 is mandatory (but i just was doing browsing/keyword search
over RFC8446). COnditional text such as:

"implementations which support both TLS 1.3 and earlier versions SHOULD"

make me think that TLS 1.2 backward compatibility is just optional.

Thanks
    Toerless