Indeed quite true! That's one reason I recommend dark meat - it's more moist in the context. The onions help keep it juicy as well. Indeed it's best to grind up the blend only enough to combine and chop the ingredients together, not to emulsify them. Pulsing the food processor helps control that.
Thigh meat especially is moister, and therefore also tastier. I use a grinder, but when I make salmon burgers I use a food processor and pulse.