I think what’s confusing here is that there are two mental models that use the word “type” in an opposing way: if you think of types in terms of set theory, then “subtype of type A is a subset of type A”. But if you think of types in terms of a class hierarchy (like in Java), then by saying “subtype of type A is a superset of type A” you actually mean “an inherited type (class) that is further down in the class hierarchy has the same or more properties than the parent type (class) that is further up”.

So I actually would agree that your original statement is valid, assuming that you refer to “types” as “classes” in the sense of Java class hierarchies.