According to the 2020 report on Property constraints (T244043):

The name of this constraint type may be considered inaccurate or confusing for two reasons:

• rdf:type is an RDF property to state that a resource is an instance of a class, but the type constraint type is also used to specify that a resource should be a subclass of another class, for which rdfs:subClassOf is used instead;
• the word "type" is already used to refer to Property types (ExternalId, String, etc.), value types, entity types (Item, Lexeme, etc.) and, most confusingly, constraint types.

The name "subject class" is proposed, since this constraint type is used to specify the class of which the subject entity is an instance or a subclass. Likewise, for the current "value type" constraint type, the name "value class" is proposed.

See also: T244053.