Ya this is why when you harvest and jar the bud up you need to burp the jar daily. Infact I just jarred a harvest yesterday that before hand was crispy dry went to burp it today and they weren't crispy anymore lol.
If you don't burp you risk or probably will eventually grow mold in there and ruin the batch.
As previously stated they dry from outside in. The point of jarring is to let the dehydration process happen evenly and thoroughly. This way when it goes through Rapid Decabroxilation (setting it on fire) it is more efficient and less wasteful. This is why it is more potent after a propper cure.
To be more specific. Cannabis does not have THC in it. It has THCA ( Tetrahydrocannabinolic acid - Wikipedia ). When decarboxylated the THCA turns into THC which is what will get you high. Decarboxylation ( Decarboxylation - Wikipedia ) happens at about 240 degrees Fahrenheit and above for THCA. So this is why a vaporizer works without burning a plant. If you run air by it at about 280 degrees you will convert the THCA and you can get high without burning the plant from whatever you can get off the surface.
Now if a plant is still wet at its core it will not quickly burn and smolder. THC is flammable so if you can't burn the flower fast you are risking wasting it. Lots of the stuff in the wet part is just wasted as the bud is smoldering and burning it in place not letting it out.
Have you ever had a bag of weed that was too dry and you added an orange peel or some lettuce to let is get a little moistened again? So when you cure you are basically doing the same thing. The flower you are putting it in a jar is out-gassing water vapor and letting the water from the core fill the jar. Then the outside which was dry gets rehydrated. Then you burp the jar and let the water vapor out. then the outer stuff drys again and the process repeats. In this way you slowly and evenly drying out the entire thing including the core. When you do this correctly when the jar stops having soft weed and gets dry you can be assured the inside of the flower is also dry. Then when you burn it the THC will come out fast.
If the core is still moist it just wont burn well and much in the core is wasted.
If you do not jar it and air dry it then it can dry out brittle and uneven. It will still eventually get there but you have no idea when really.
By jarring and burping you can monitor the process and know what you fell on the outside is the same as the inside.