"Counterfeit postage" does not mean just stamps, in means any
counterfeit franking which may
include postage stamps.
A read of the article indicates much of the counterfeit postage came from an out of date meter:
The postal inspector said that the shipping labels used a meter number which had already been phased out of use in 2020, even though they also indicated they'd been purchased in 2023.
Within the boxes being shipped were found counterfeit postage stamps