I suppose, in the same way that Dylan Roof is the fault of some Conservatives, or some Southerners, or some Americans, etc. Yes, the existence of terrorist organizations that make use of these lost angry men means that in a minority of these cases a group can tell them to attack on the same day rather than weeks apart, and means they can stamp an ideology on them, like I said. So yes, there is a difference, just as there is a difference between the shooting that are done by a couple of friends (like Columbine) and the ones done by a lone wolf (VTech).
Still, people don't find it inappropriate to bring up Columbine when they talk about VTech or Aurora. When people try very hard to exclude all the other mass attacks and single out only the ones connected to Islam in situations like this speaks more to their personal biases than anything else.