While I agree with Mr. Kearney that it's better to "do it right" in the
first place, I seriously doubt a length of wire would pose any more
hazard in a fire if it was located on the outside of the siding or
underneath it. I've never heard of a cable acting as a "fuse". There
are far more combustible materials used in home construction and I doubt
the "fuse factor" would be pose any real issue. I mean, by the time it
gets hot enough to ignite FT-4 or FT-6 rated jacket, the vinyl siding
would be ablaze as well.

Suit yourself, quite possibly 'law-suit'.

Code exists for a reason. It's all a bunch of little stuff, but much like
the death of a thousand pinpricks, it's the little stuff that adds up. Just
because your one wire isn't a problem doesn't mean it won't become part of a
larger problem later. I've seen and heard tell of all sorts of wiring
stupidities, some DIY, a fair bit by "professionals". I'd rather avoid
doing something lazy on the premise it "might not" be a real problem.

Really, your home is probably the most expensive investment you'll ever make
in your life, why screw around with it? Why put your life and your money at
risk? Just to be cheap/lazy? Honestly, it makes no rational sense.

But hey, feel free, someone's gotta keep the firemen, lawyers and morgue
clerks busy...