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if you take the side of the open cabinet you took a photo off, the side attached to the wall where he took the tiles off, he should be able to reduce the width or the top/bottom and shelves and put back the side to make it fit.
I can’t imagine you would need to order that section again, just narrower, and swallow the cost. From the photo it looks like it’s a separate element. Potentially, lose that bit completely and have him build a ‘frame’ around it to make it look built in.
We had quite a few cabinets created and while some could be pre-cut and pre-assembled there was always allowance to create a frame around it to make it fit as you can never go by measurements only (uneven walls, allowance for cabinet doors etc). An experienced carpenter would know and allow for this.