It could be old stock - - or - - Miken/Worth has had so many issues/problems (uncountable) with durability that they changed the composition to help the bat last longer. At one time nothing could out hit a Miken but those days are gone as the field is pretty equal with most other bats hitting just as/if not further with a longer life.
I quit buying them because of it - you can "sound" out the bat by hitting the knob on the ground and listening to the tone of the bat like you would a tuning fork (2 fingers on the barrel softly) and bring it to your ear. The lower the tone the longer the break in period (good news - the longer it will last - thicker wall)....sound out some team mates too so you will know the difference from your new bat to their game ready bat and judge accordingly.
The higher the tone the more "open" the bat is - if it has that tone and no performance you might have gotten a dud. When I bought one with a high tone & the performance was good I was lucky to get 60 contacts out of it.