"Is dispensary cannabis not the same as home grown cannabis?"
Assuming that I get the same plant (genetics), and have one grown by a commercial grower, and I grow one myself at home, they're going to be somewhat different. Deciding factors will be: What sort and how much light I use, growing method, processing method. If I had to pick the most important factor determining any differences between the same genetics, it would have to be the light. More light equals more energy equals more growth equals better bud development equals better effects, up to a point. I don't think there's anything different about the stuff coming out of commercial grow operations compared to what I can grow at home that can't be accounted for by the differences in growing methods and light received. My homegrown Northern Lights is markedly different from the greenhouse grown Northern Lights I can buy from the stores here, because my stuff grew outdoors for the season under the sun, instead of also being supplemented by LED / HPS lights when the days get shorter. Different, not better, not worse. It's clearly the same type of cannabis, it just grew differently, and as a result, expressed certain traits more or less.
No, I don't think there's anything different or special about dispensary cannabis. If you replicate their growing and processing methods down to the T, you will end up with the same "dispensary cannabis" right at home. Of course that's vastly impractical in most cases. Any perceived differences probably just come from the way it's being grown and processed. I briefly worked in the Canadian cannabis industry, and the volume of cannabis these greenhouse operations are moving is making my head spin (literally, as you will be perma-stoned on the job, as a result of handling sticky-ass plants all day).