I've installed maybe five in twenty-five plus years. It's not something I think about much.
Had a customer with quite a bit of plumbing for me, upgrading several bathrooms. They had purchased the Totos well in advance, one of the skirted models that require the cleats, with the screws going in through the sides. First two went fine, the third one went upstairs in a bathroom I hadn't seen before. I did all the prep work and tried to install the toilet, but it would not fit. I checked the dimensions and yup, it needed a ten-inch rough toilet.
Lately, they called and said they had the ten-inch in hand, and wanted me to come back and install it. For free. I told them no; if I had purchased the wrong toilet, it would be on me. Since they bought the toilet it's on them. She called back several times and got the same answer.
Ordinarily I might have had a little more sympathy for them, since they were not aware of the dimension issue either, but add to the fact that I had to pile tools in the bathroom doorway to keep her from coming in and pestering me to death through the whole job. Her husband was a world class micromanager also.