It may not be correct to speak of a "wallet", but I do think it is useful to do so. The idea of a wallet communicates that it contains something of value that must be secured, in this case that would be your private key/ seed phrase. If you want to get philosophical it is what Wittgenstein would call a " language game". Also the meaning of words changes as the world evolves, and with increased bitcoin adoption the meaning of the word "wallet" would change to include the apps that are called wallet.