Binding issue could very well be installation related. This would make it more unforgivable. He took the bike in, they serviced it after brand new and it left the shop with the same issue. This is pretty unforgivable really...whether the shock is at fault or the installation. Question is...does the shop have any idea what they are doing? So far, doesn't sound like it. Likely the shock could bind if the two competing screws on the side aren't torqued properly...two high a torque...or...very unequal torque on each side.
But it could be a shock issue. Shouldn't have left the shop uncorrected the first time is the point.