TLDR: The 6 months rule does not apply to valid OCI holders with Canadian passports. I was able to travel back in India with my passport expiring in less than 6 months and an OCI.
Details:
Before I undertook my journey, I had some family & friends travelling to and out of India. I asked them to ask this question to immigration officials(as no one else could answer). The answers I got made me feel very comfortable to be able to travel to and out of India in my situation.
Then I myself asked the immigration official on IGI International Airport about this rule. They said it does not apply to OCI holders. I was told that I could enter India as long as my Canadian passport is not expired.
I was told that the rule could apply to someone with a visit/tourist visa, but even then there are 2 cases:
1. If you have more than 3 months passport validity, you will be allowed.
2. If your passport is expiring in less than 3 months, then they will "look at your case" - in this scenario you have to "request" the supervisor on the Airport Immigration and most likely they will let you in based on your case.
My personal feeling is that for case #2, one will be allowed if:
a. They hold a certain passport and can prove they will leave the country before the passport completely expires(by showing return tickets, etc).
b. Telling the officials that they will renew their passport while they are in India - which is quite realistic.
If you have this scenario, I would advise you to travel through a major international Airport, not a small one. The immigration officials at major International Airports are much more well versed with such scenarios.