If you start with a whole tile in a corner, then the walls need to be very straight - they often aren't - which will throw all the subsequent tiles out.
If you start with a whole tile in the corner, what happens when you reach the next corner? Those tiles will most likely need to be cut and you do not want to end up with a very narrow row of tiles.
I had larger tiles in my bathroom and they were planned to be evenly spaced on either side of the window over the sink and also planned so that they did not leave a very narrow tile at the top of the wall, or just above the sink or where the tiles meet the floor. So all four corners of the bathroom have cut tiles of slightly under half the width of a full tile and it doesn't look bad or wrong and the spacing around the three sides of the window and the window sill look pleasing.
Had the wall with the window in it started with a full tile (either on the left or right) then the spacing around the window would not have been symmetrical.
https://www.tilewarehouse.co.uk/help-advice/how-to-set-out-wall-tiles/
Planning the layout of your tiles
It's important to plan where you'll be laying your tiles. There is no hard or fast rule, and it will often depend on things such as the positions of windows, walls etc. but it's often wise to use the natural focal point of the area to be tiled and have this as your starting point.
How to set out wall tiles a step-by-step guide
Step 1: Start at the centre of your wall
It's always advisable to start tiling your grid in the centre of a wall, as it's easier to make sure your pattern is symmetrical. It also means any half-tiles you may need can go at the end of each row and will be of matching size.
While it's tempting to begin in the corner as you would when painting, it may leave you with wonky rows and a messy finish by the time you're done (which no one wants!).