Interesting. I insert the flyline into the core of the buried tag as described in step five and find that I get a good transition from the line through to the loop without a hinge at that location. I wonder what’s different. In fat lines that won’t go into the core I will strip the coating off the last inch of the fly line to expose the core, then insert the that piece of flyline core up into the buried tag. Generally I have only had to do this with floating lines 10 wt an up.
I once had a braided loop slip off while playing a fish. Since then I have used Pliobond to glue (1) the tip of the line inside the braid and (2) the ends of the braided section under the sleeve that slides down to hold them in place. Haven’t had a problem since I started using the Pliobond, and it is flexible enough that it hasn’t caused hinging either.