Yes there is a difference. The difference is knowledge and experience in the particular field where project management is needed. Certainly you would not hire a project manager that has managed the construction phases of a large building to be a project manager to develop a software solution for something as complex as a paper or document management system.
An IT project manager must have years of experience in the information technology field. Since project managers are often required to estimate the time a team should take, to develop a solution, and estimate associated costs, it just makes natural sense.
Software developers suffer a bad name when companies hire project managers who don't have years of experience in the IT field and they grossly under estimate the length of time software development does take.
In addition since project managers are very often involved in hiring technical staff, what happens when they hire poor system administrators or developers?
Would you hire a student to build you your brand new home? Then why on earth would you hire a student to build you a complex business solution who doesn't understand the first thing about ERPs? Sure my nephew builds web sites. How often have we heard the same story over and over again of the years it's taking my nephew to finish my site. Just because a kid says they can build you a web site, if they don't have years of experience, you would not be considered wise if you hired them to build something only an expert should have taken on. As the old saying goes: "Expectation unfulfilled makes the heart sick". The same goes for hiring the right Project Manager for the type of Project. So, just like you wouldn't hire a kid to build your dream home or hire a profesional machinist, to do so, who has not framed homes before, you couldn't expect a General Contracting Project Manager to build you your dream IT solution. Neither would you hire an IT Project Manager in place of an experienced Aviation Project Manager, would you take the first test flight? I didn't think so.