Customers has usually have their maintenance contracts for period monthly or year and are supposed to create some time with back date plan date as well. The System should behave as per the plan setup (meaning if users setup the schedule to plan date, it must schedule as per the plan date, no other date should be considered!!!).

With the current behavior of D365, When using the Interval type: Repeated from plan date on the maintenance plan line, then next scheduled maintenance will be planned from that date and not on that date. To get a planned maintenance line with an earlier date, it is possible to back-date the plan date on the maintenance plan but the system will only generate a schedule line with a plan date that is greater then the date when the plan is run.

The expectation is that when the users should be able to choose plan as back dated as well and when creating maintenance schedule the system should consider the plan date based on the user selected.
In practical with period frequency year means customers will expect to have expected start date from plan date not from the one later to start the manintance schedule.