Yorky1

Thanks wefalck.  That's what I was thinking.
I also just received a reply from Captain Watson of the current Bluenose II and he says that rigging has changed a bit through the years and he explains this is currently how the Bluenose II is rigged:
   "The clew line block is simply seized with small line to the starboard side, on the becket on the lower portion of the single halyard block at the head of the sail. This is where the sister hooks attach the sail to the halyard. The clew line leads from deck through a fairlead attached to the middle of the forward side, of the aft spreader, through the clew line block (leading forward aft), through a grommet in the middle of the sail and then to the clew. 
When the clew line is pulled, the clew is pulled to the sail grommet, then both to the head and all of it is pulled to the head of the lower mast where the hoops on the topmast come to rest when the sail is in the lowered condition. This means that the head, the mid sail grommet and the clew are all together at the lower mast cap. 
It should be noted that the grommet arrangement has changed over the years and on different schooners. The single grommet in the middle of the sail is what we use now. "
 
* So it seems the Bluenose II crew now seize the block to the lower becket of the halyard's single block, so the clew line load is taken up directly through the tackle to the mast, rather than pull on the sail's peak grommet.  See attached drawing.
With this in mind, looking at the Jensen drawing again, it now looks to me like the block's strop/eye may have been taken to the sister hooks at that time when the book was created; again the load would have been taken directly up to the mast and not through the sail's grommet. It is also possible that the Jensen drawing is depicting the very same method that you describe. It's a pity that Jensen did not write the exact method or draw it in close-up .
 I think I will amalgamate all this information and form an eye then attach it to the sister hooks. I doubt anyone will ever notice the detail but me.
Thanks to all who contributed here!