A gang of harmonica geeks saved the soul of the blues harp (2013)
collectorsweekly.com
collectorsweekly.com
https://www.youtube.com/watch?v=2fayFSiceZA
The hardest skill to master on a harmonica is playing one note at a time without bleeding into the holes on either side. Once you master single hole pucker, introducing the side holes adds more texture and harmony at your discretion. The second hardest skill is "bending" by changing your embouchure and air stream flow to bend the pitch of the reed. You can't really effectively bend until you single note pucker since the reeds bend at different rates which only sounds good when you've mastered both skills which are key to a good cross harp player.
If you decide to get a harp for starters the plastic Hohner Marine Band harp is super tough and forgiving. The more expensive wooden comb blues harps sound amazing but they take some skill to master.
Diatonic harmonicas are keyed, where the "C" note (4th hole blow) can be in any whole tone, so some transpositional thinking is required once you get good. If you want to play cross harp (aka "blues") with a guitar player typically playing in the key of E, then get a harp keyed in A.
That "single-note pucker" is something I never even thought about. I use tongue-blocking, and I can still bend a note. I should note here that, at the time, I didn't even know there WAS another way to get a single note, so that's what I did.
I'm not saying you're wrong. I'll just note that he says he can't quite master bending, and he's doing the pucker.
Mark Twain actually called out that as a New Orleans word.