Since life or evolution is basically self-replication with variation in a shared environment, any mechanism that can carry information forwards can and probably will be used, or has been in the past. From that perspective, some phenotype changes are trivially genotype changes. (Eg anything that changes the egg-cell, will influence the life that grows from it.)
It is weird to expect only DNA to be used. The process is not that orderly. The special thing about DNA (and a few other mechanisms), it is invariant to phenotype changes. And that it will copy over information that has no direct influences on self-replication. That is what enabled unlimited heredity.
It is weird to expect only DNA to be used. The process is not that orderly. The special thing about DNA (and a few other mechanisms), it is invariant to phenotype changes. And that it will copy over information that has no direct influences on self-replication. That is what enabled unlimited heredity.