First for the record LIGO scientist made the claim in a press conference and it's on their web page.
Second , So what?
A proton is orders of magnitude shorter than the smalle wavelength photons.
A 1/10000th of a proton radius is .88X10^-18 meters.
A femtometer is 10^-15.
Gamma wavelength photons are 1 picometer.... which is 1000 X 1 femtometer
In short,
They are saying the can measure in units a millionth of the shortest wavelength of a photon.
It will not perturb the proton to enough to measure what it did. Much less a displacement of 1/10000th of the protons radius.
I won't even get into the various types of "noise" whose range is well beyond that tiny scale.