As I said two different colours can't come of the same batch,. Sizing on tiles is usually nominal so one batch 300 x300 can be 298 x298 and one batch can be 304 x304 as for thickness there probably is some variation also , but that being said if they couldn't do a good job with what they had they should of said. .
Some adhesive goes of quicker than others also depending tile type ,temperature , humidity , and background . I have certainly walked in tiles a lot quicker than a couple of hours as was stated earlier .