the builder is correct, however, for the wrong reasons.

ANSI specifies and NTCA standard is offset on any tile with one side longer than 15" to be no more than 33%.

Why?

(remember we are talking ceramic here and not marble/stone)

because the standards for cupping is measured in percentage... 1% across the smaller tiles we traditionally use is nothing, but 1% across a 2 foot tile can be a noticeable crown! To put the high arch of the cup, the middle of the tile, against the lower corners can present considerable lippage, especially if a leveling system was not used! Not all tile is made the same, some cups more than others...

I will always test the tile in the field, put 2 tiles face to face and see how much they rock on one another. If it is bad, consider a pattern other than a running bond! if it is medium, i will use my Tuscan Leveling System to hold the tiles together.

The edges of the tile and the the size of the grout joint also affect perceived lippage. the grout joint is based on the irregularity of length of three tiles. What ever that offset is, multiply by 3 and that is your grout joint. By widening the grout joint, you eliminate the lippage.

here is a foyer i did with 12 x 24's in a running bond in West Orange, NJ. The cuppage was medium so i used my leveling system and the result was a dead flat floor!



these other pics are during install, you can see the clips i use. The orande stuff is Schluter Ditra, a premium uncoupling underlayment we try to use on every job.