Flyline/Leader Connection Question

Sure, but you can apply the argument backwards:

If your fly breaks off you use a better knot. The next thing that gives is you
bloodknot (if you make your own leaders), so you improve that. Ultimately what
you want is a leader system where things break at the
strenght they are supposed to and not at 50-60% of that. Off course at some
point you have improved each
section such that the thing that breaks is your tippet, without having to
improve the butt and line connection.

As long as you know how your leader is designed and that it does what you
wanted, then fine.

Wrt the leader/line connection the nailknot is between 70-80% of leader butt
strength, but
the braid is 100%.