You've shared the real life hack.
My kid was born with a love for the opening theme to "Star Trek: Enterprise", because we were bringe watching it while the kid was in the womb.
Playing "Faith of the Heart" came in handy when the kid started teething.
This is great advice.
I've always done this, and my kids all started talking surprisingly early.
But my motive is just that it calms them.
Some baby fussiness comes from insecurity, and I find that a running narration makes them more relaxed about being set down and returned to - that kind of thing.
Basically they get the same comfort from my narration as I get from leaving the TV running when I'm alone in the house.
I don't know (or worry about) if it really makes any serious long term difference - but it was occasionally convenient as heck when they could tell me what they wanted a bit earlier than I (or anyone) expected them to.
With my last kid, I felt more brave and also mixed in some singing, and think they are more musically inclined because of it.