It says that on mine also, but I received 50% off the annual plan (code) and paid for it with Gift Cards, so I do not know if that has something to do with it.
They are changing how to access Showtime this summer, basically to where who can access Showtime programming in the P+ app, pricing supposed to be $2 more for the Commercial Version and $5 for the Commercial Free Plan.
Paramount (formerly ViacomCBS) is combining Paramount+ and Showtime in a single, integrated streaming offering starting this summer.
deadline.com