Otherwise, just take more tiles and cut two baseboards of 5cm each from every tile. These will then have perfect edges. I don’t know of any rounded cut. I also wouldn’t know how that’s supposed to work or look with porcelain stoneware.
That’s how it is, the tiler simply does it that way. He cuts one strip off each long side, the rest is waste. It can’t be done otherwise, because you would otherwise have sharp edges. The completely normal solution from fits. I wouldn’t buy ready-made base tile strips for such a price.