Honestly it never occurred to me to even look for such an app.

It may simply be that this is built-in and thus more people will have/know about it.

I can't really say because I haven't used either Apple's live listen feature or any of the microphone apps on Android, but the article says live listen doesn't just amplify sound, it isolates and amplifies voices. Which sounds like a different thing to the standard microphone apps.

Yeah that's pretty similar to what current/last gen hearing aids can do. My mother has been dependent on her pair since she was 7, but a few years ago she upgraded to a newer version. The hearing aid has a few different modes for isolating foreground and background noise toggled by a small button. There's a general amplification mode, conversation mode (isolates) and a crowd mode.

Now I'm very curious as to what current gen hearing aids are capable of.

The focus on low latency is a big deal. Many of the live mic apps are fine, but they have noticeable lag (really low, but there)

But also being built in is big too