I suspect it's as much to do with pressure and gas volume as actual velocity. The 22 Hornet only has a 43,000 CUP SAAMI max pressure. So if a guy is loading his Hornet to hotter levels, he might blow the can off the end of the barrel.
Like you said, it's worth a call to Silencerco. Let them know what you have in mind and see what they think. Because I wouldn't want to be "that guy" who bought a can and waited 11 months, then blows it to pieces the first day out.
Edit: Perusing the Hodgdon 22 Hornet data, it looks like the famous 13 grains of Lil' Gun with a 40 grain bullet for ~3000 fps is quite mild on pressure. Well within SAAMI specs. So rock on!
