Not sure if this changed since the original post, but I had the same problem, this is what I found ultimately in sf help.

https://help.salesforce.com/articleView?id=process_limits_scheduled_processing.htm&type=5

If the Process starts when the record is Created, then it doesn't re-evaluate. If it starts when the record is Created or Edited, "scheduled actions remain in the queue only as long as the criteria for those actions are still valid. If a record no longer matches the criteria, Salesforce removes the scheduled actions for the record from the queue."

Though, another part of that page points to another problem. If you de-activate the Process, change it, and activate the new version, "the scheduled actions continue as usual. If a deactivated process has pending scheduled actions and the record whose field the schedule is based on is changed, Salesforce recalculates the schedule for those actions. Once a process is deactivated, Salesforce ignores all other changes to associated records."

Not sure if this changed since the original post, but I had the same problem, this is what I found ultimately in sf help.

https://help.salesforce.com/articleView?id=process_limits_scheduled_processing.htm&type=5

If the Process starts when the record is Created, then it doesn't re-evaluate. If it starts when the record is Created or Edited, "scheduled actions remain in the queue only as long as the criteria for those actions are still valid. If a record no longer matches the criteria, Salesforce removes the scheduled actions for the record from the queue."

Though, another part of that page points to another problem. If you de-activate the Process, change it, and activate the new version, "the scheduled actions continue as usual. If a deactivated process has pending scheduled actions and the record whose field the schedule is based on is changed, Salesforce recalculates the schedule for those actions. Once a process is deactivated, Salesforce ignores all other changes to associated records."