TFW Merriam-Webster is writing about the same thing you wrote about:
It’s a discussion of no problem and other phatic expressions which are more informal than you’re welcome and also seem to imply that saying thank you was not necessary. M-W didn’t pick up on my predating of you’re welcome but that’s probably for the best. They’re the professionals, after all. Check the M-W article here.
In other news, this morning my 9-year-old texted “no problem” to me after I thanked him for something. Kids these days. Pssh.