here's a revision which documents the past rather than constraining the future:
Additional methods may be defined as specified in [SSH-NUMBERS]. The
name "diffie-hellman-group1-sha1" is used for a key exchange method
using an Oakley group as defined in [RFC2412]. SSH maintains its own
group identifier space which is logically distinct from Oakley and IKE;
however, for one additional group, the Working Group adopted the number
assigned by [RFC3526], using diffie-hellman-group14-sha1 for the name of
the second defined group. Implementations should treat these names as
opaque identifiers and should not assume any relationship between the groups
used by SSH and the groups defined in 2412 and its successors.