From RM 1.0.2 common.pdf section 5.1 (https://specifications.openehr.org/releases/1.0.2/architecture/rm/common_im.pdf):
A FOLDER instance contains more FOLDERs and/or items, which are references to other (usually versioned) objects
Note the “usually”.
The description in RM 1.1.0 is the same (Common Information Model) but the UML clearly shows a binding of the items OBJECT_REF to VERSIONED_OBJECT, which determines that the reference is not to a “usually” versioned object, it is always that way.
So somewhere between RM 1.0.2 and 1.1.0 this was changed and the change log wasn’t recorded. Note this is a breaking change if any FOLDER.items reference to a different object type than VERSIONED_OBJECT, like directly referencing a COMPOSITION instance in 1.0.2. With this UML that reference won’t be possible in RM 1.1.0.
This is similar to what @sebastian.iancu mentioned here What's allowed in FOLDER.items - #11 by sebastian.iancu because they implemented items without the constraint that was added to the target in RM 1.1.0 (or maybe before that?)
In any case this is a subtle breaking change that might affect many for ended up kind of silently in the spec.