Whopity, of course you are right. The problem is, that LevelAttitudes claim
You cannot because it is not specifically allowed
is, unfortunately, both technically right and simultaneously nonsensical.
The issue is that the "anything is permitted that is not prohibited" type of regulation wording of the JAR FCL, which said that
Originally Posted by JAR-FCL 1.300
A person shall not carry out the flight instruction required for the issue of any pilot licence or rating unless that person has...
was replaced with
Originally Posted by EASA-FCL 1.900
A person shall only carry out ... flight instruction in aircraft when he/she holds....
and whoever then wrote the rest forgot to include a lot of types of instruction... which is, beyond philosophical issues, the biggest problem with this approach to regulation.
Meanwhile, in the real world, the following applies:
Originally Posted by Common Sense
Anyone can teach anyone anything, as long as they don't do anything stupid. For it to be allowable for anything formal, you need the appropriate rating. If that does not exist, shrug your shoulders and use the most appropriate one.