Be careful, that is a decade plus old expired draft of a proposed update to RFC 2606. The current version of the standard, including 6761 which updates it, does not reserve most of those.

https://datatracker.ietf.org/doc/html/rfc2606#page-2 https://datatracker.ietf.org/doc/html/rfc6761

You are probably safe using names like .lan and .corp but they are not currently protected by standard in the way example is.