Try and improve the understanding of room versions

specification/index.rst

@@ -430,6 +430,13 @@ upon through new algorithms or rules, "room versions" are employed to
 manage a set of expectations for each room. New room versions are assigned
 as needed.
 
+There is no implicit ordering or hierarchy to room versions, and their principles
+are immutable once placed in the specification. Although there is a recommended
+set of versions, some rooms may benefit from features introduced by other versions.
+Rooms move between different versions by "upgrading" to the desired version. Due
+to versions not being ordered or hierarchical, this means a room can "upgrade" to
+version 1 from version 2, if it so desired.
+
 Room version grammar
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