This is a minor bug i just discovered.

I was in my privete server with the 15w50a snapshot and had a flint and steal in my 9th spot then i switched to any of my tools in my hotbar and had to wait double the time to get it out and use it

For example:

I have the "Flint and Steal" in the hand and then switch to my "Sword", the sword charges up once but then out of nowhere starts charging up again immediately