`return` may be a valid statement but an object literal is not.

A standalone object literal would likely be interpreted as a block and would throw a syntax error unless it were a simple identifier and a statement `{ foo: <statement> }`, in which case it would not interpret it as an object but exactly what it is, a label and a statement.

This is why JSON parsers which use eval must first wrap the object literal with parens, to make it an expression rather than a statement.