The warning is the same for the XC40. Does the car really care what size the wheels are? The main consensus on that thread is that the software update isn't necessary. Do you really want to traipse over to the dealer every six or so months?
The difference in circumference can be practically nothing. For example, if you go from the 20" R-Design tyres (245/45/ 20) to 18" of the same size that Volvo uses for their winter tyre/wheel packages (235/55 R18), the 18 inch tyres have a circumference that's 1.7% less than the larger tyres. If you plug these figures into a calculator like
https://tiresize.com/comparison/ it says that this will make the speedo over-read by a whole one mile per hour when you're doing 60 (so you'll actually be doing 59 mph).
For such a difference, the software update isn't worth it.