Public key verification is ultimately needed in all end-to-end encryption systems to offer a strong guarantee that the conversation is not subverted by a man-in-the-middle attacker. If can be done by using the Socialist Millionaire Protocol (https://en.wikipedia.org/wiki/Socialist_millionaires) and a shared secret, but more often the verification is arranged in-person, out-of-band, manually.

As realtime, realistic voice synthesize is thought to be difficult, a voice/phone call encryption system usually circumvents this problem by using the caller's voice as the proof, as both recognize each other's voice. In most phone encryption systems, like many commercial systems, or the ZRTP protocol by Phil Zimmermann, or the "safety number" in Signal, they allow both parties to read out their pubkey's SHA-256 hash digest (usually encoded to words) aloud, as a mean of verification.

If this type of AI-based voice synthesizer becomes widely-available, it could be disastrous to cryptography. It is not the end-of-the-world of course, as targeted attack with social engineering is not an issue for most people, and those who need this level of security is going to perform out-of-band exchange anyway, but still, the certainty of voice-based key verification would be greatly weakened.