It is scanning. Just like with wet printing you can get very different looks from the same negative. I have a home scanner and get very different looks for the same Portra picture just based on different scanner software settings.
The scanner software I use is Siverfast, and for example, turning on "automatic color correction" can make a huge difference, not always in the right direction. Also, there is a big difference between scanning using the different Portra profiles (VC or NC; Silverfast doesn't have a profile for the modern Portra 400).
I actually hate all this choice because as with other digital PP (e.g., digital camera files) I can't get a consistent look and I often can't decide on an obviously better version. I suppose that's what you pay a lab good money for.