Your pedantry is "almost" correct. ;-)
The only program that is bug-free is the trivial one liner.
NOP // assembly no-operation
Though some would argue:
is bug free since without input, and output, whatever "calculation" you do is pointless & void.
Software runs on the _assumption_ that the hardware is
a) functioning ...
b) ... correctly!
We have almost no way to guarantee that in software. Sure we have ECC RAM but what else? Anything more then 1 line is making these assumptions and therefore is a candidate for being buggy.
So I would revise your statement:
"All non-trivial software is buggy."