I have not seen any rubber seals that did not use the lock strip, front or rear.  I would not go by Haynes but by the factory manual and the suppliers like our host. 

Our host sells rear seal JRC2674 which says it is for all Minis and uses lock strip 24A1466.

It definitely had the locking strip in the first place, and although it was a bear to put in from the outside with the threading hand tool, it definitely was snugger once the silver locking strip was inserted.

I've since seen a way to install where you fit the glass AND locking strip FIRST and then you loop a cord through the channel that the car body is supposed to go into...but..

[ EDIT: I HAVE REMOVED THE HOW TO STEPS FOR THE CORD METHOD AS MORE RECENT POSTS WARN OF A DANGER OF TEARING OR DISTORTING THE HEADLINER IF THE STRING METHOD IS USED] The YouTube video that I saw that method in never mentioned the danger, but in retrospect it makes a lot of sense.

And it goes without saying (but I'll say it anyway) if you take the old gasket out, peel up the headliner and inspect underneath for rust, treating anything you find and re-gluing the headliner.

Never put a new seal over rust-bumpy metal. It's like sealing it into its own private little "make more rust" party room.

The groove is there for a reason. I would imagine the seal would leak like a sieve without the locking strip.

I noticed the strip that goes into the rubber seal around the rear window was missing on my mini.  Thinking it must have fallen out or something, I ordered a new one.  However, when I look at the Haynes manual, it says the rear window does not use the locking strip?  Why would the front require one and not the rear?