The inspection is intended to explain the IDE’s behavior in the cases when both the class and the class alias declarations are present. When several declarations with the same FQN exist, the IDE usually fails to choose a single one between them. This leads to missing code completion, erroneous type inference, etc. But since the class declaration prevails over the class alias declaration, the latter becomes redundant and therefore ignored by the IDE.
Please note that the ignoring class alias declarations does not affect the behavior of the PHP interpreter.