You may also be getting too deep into the weeds on hyper accurate texturing. Sometimes it just needs to pass the smell test and you move on to bigger things.
Also, are your dimensions of the wall to the outside of the frame or the brick? Many times the dimensions are to the outside of the frame and the masons can take one look at the wall and know exactly how to lay the bricks out to make it look correct. The masons I've worked with in the States when I was a residential framer back in the day, they are so good at what they do they can score and chop a whole pallet of bricks before you could even ask them how they do it. You are also assuming that in a pallet of bricks they are all the same size, which they are not and the good masons can spot these irregular sized bricks and know how to use them to make up odd dimensions here and there. Plus most masons have apprentices which those are the poor sods who have to do all of the hard cuts. The master mason just hands the apprentice the cut sheet, gives a good slap on the back, and walks away laughing.
The issue arises in the CG world where our textures are indeed perfectly sized bricks with perfectly space grout and that just doesn't really happen in the real world. There are subtle differences that most people will never be able to tell unless you use a laser to measure, but those differences mean that they can make the bricks fit odd dimensions a lot easier than us using our perfect textures.
