DSG notice on occasions, the same Gear and Speed has different RPM

I have recently picked up a second hand Golf mk7 2.0 TDI (150) with DSG MY2014, and today noticed that when driving at 70 MPH in 6th the RPM was almost 2,200. However, in the past it's been just below 2,100. So I switched the Cruise Control off momentarily and re-engaged it again, and the car sped back to 70 MPH, but this time was just under 2,100 RPM as normal. Has anyone else noticed this?

I know speedo's can be off up to 5%, I wonder if this is what you are actually seeing. Only way to know for sure would be to log via VCDS or something.

According to my experience, in same gear and speed, more drag force means more RPM.

Thus, wider tires, less tyre pressure, upslope, wet road, all these may cause a higher RPM.