I've said nothing so far on this...but i am sure that the decision
to segregate the tyre area into 2 distinct 'zones', one repairable
and one not, has not been made lightly, or without the input of
the tyre manuafacturers.
Sure one can 'assume' that they're only in it for the money by
saying it can't be fixed if it is in the outer band of the tread, but
realistically, they could just as easily have said no puncture
can be repaired....and given umpteen real/made-up/imaginary
reasons as to why.
Safety is paramount, and based on that fact alone I have to say
that I agree with the guidelines, in fact, I quite recently had to
replace a 205 Hankook wtih a screw in just such a place/position
as greg2k's that had more than enough tread for many
thousands more miles. And not only that, I replaced the tyre
on the other side of the axle at the same time as I would rather
have equal amounts of tread n grip n life on each.
Those facts were the basis for the decision that I made, not that
I have too much money, or....more money than sense.