First a small clarification: a Divemaster is NOT an Open Water Instructor.
I checked everywhere I could think to look, and did not find any PADI guidance on interrupted training. I swear I have read it in the past, just couldn’t find it. The one year limit that sticks in everyone’s memory I think comes from the paperwork limitations, and the stated “one year from last completed activity” on a referral. But I am pretty sure there was a specific article clarifying that interrupted learning does not have to start over again, but does require some common sense review and remediation to finish up.