Actually it does play a factor, GDPR had it so the data on EU citizens had to be located within the EU. Now they have alternative options for the UK - then that aspect does as I initially outlined becomes key.
Hence the question of actual costs to Google in hosting in say Ireland (staffing, taxes, rates, utility costs, cooling....) compared with another location outside the EU that may very well have cheaper running costs due to many factors.
I hope that clears up why location is a factor now as it related to running costs and if they can save some money, well, they will.
More so if they suddenly free up capacity in a datacenter which has higher costs than some other locations outside the EU. All these details do very much, however small, stack up at the scale of users Google operates with and for the UK, several million is a large chunk of potential savings.