What happens if a transaction does not signal replaceability but spends an output from an unconfirmed RBF transaction?

Question

What happens if a wallet spends an output of an unconfirmed Opt-In Replace-by-fee (BIP125) transaction, but does not flag the spending transaction as Opt-In Replace-by-fee?

Receiving wallets would see that transaction as a non-RBF transaction, while it actually is, because its parent can be replaced, making the child transaction replaceable.