Liquid Force "Adjustable Wrap T-Handle"

I'm looking into the Liquid Force "Adjustable Wrap T-Handle" (http://www.liquidforce.com/ropes-t-handle.html).

It looks like a good idea, since there seem to be very limited handles available with a wrapped grip.

But this installation photo shows that you need to put a knot in the existing handle line for the T-Handle to grab onto:


I've read that a knot will greatly reduce the strength of rope, including Spectra. Does anyone think it should be a concern? If my mainline had a knot, I would be looking into replacing it before someone got hurt...