If a user are set up in P6 Cloud Admin, but are not active and access is disabled in the Cloud Admin. Would these “inactive” users count towards their user license limit? In the client case, they have rotating seasonal workers and only use P6 during certain times of the year.

P6EPPM licensing is by  "Hosted Named User": "is defined as an individual authorized by You to access the hosted service, regardless of whether the individual is actively accessing the hosted service at any given time." so, if the user is not active is not authorized and therefore not counted.