To inspect each tile though you would have to lay them out somewhere as a whole, not practical imo. Plus who would do this if all the numbers are the same.
We don't have that natural sunlight like Italy . It's not always possible to see slight changes in 'whites' .
They were most likely from an Italian factory anyway - so it was your fault.
Sometimes the changes are so slight it's not noticeable….until you grout and then it shows up. I had it once with a rogue box of tiles. The whole palette had been checked, not by me, apart from 1 box that the details were facing inwards. Customer forgot to mention it to me and they were laid. He did pay me to remove them and relay. It was never noticed until it was grouted and then when you caught it in certain light it showed up, albeit very minimally, but once you know it's there then the game's up.
Can't really offer any new advice other than every so often you are served a great big excrement sandwich and you just have to eat it down. I ate mine earlier in the year with a BCT fail.
frankly I'm tired of saying things to those who refuse to understand.
Perhaps the rules are valid only in Italy?
go read the rules. you could avoid many headaches.