opportunity attack and different reach

just saw this 

How does a Reach weapon work with Opportunity Attack?

An Opportunity Attack is triggered when a creature you can see moves beyond your reach. If you want to make an Opportunity Attack with a Reach weapon, such as a Glaive or a Halberd, you can do so when a creature leaves the reach you have with that weapon. For example, if you’re wielding a Halberd, a creature that is right next to you could move 5 feet away without triggering an Opportunity Attack. If that creature tries to move an additional 5 feet—leaving your 10-foot reach—the creature then triggers an Opportunity Attack.

But crawford did state this If you have more than one reach, a foe provokes an opportunity attack when it leaves any of them. which means that even if you are carrying a halberd and they move five feet away they will trigger an unarmed opportunity attack, i never knew this before but will definately use it

Jeremy Crawford på X: "If you have more than one reach, a foe provokes an opportunity attack when it leaves any of them. #DnD https://t.co/tg4tGMDF0B" / X

That’s not what that means. A halberd has a reach of 10’, so you only provoke when moving more than 10’ away. 

More than one reach is something like dual wielding a short sword and a whip, where one has 5’ reach and the other 10’. In that case, moving from 5’ to 10’ would provoke an OA from the short sword. 
Also some monsters have things like a bite with a reach of 5’ and a claw with a reach of 10’. Same principle, moving from 5 to 10 would provoke from the bite.