I just tried a .csv file with no field names (from a bank) using both FMA 11 & FMA12. They both offered the choice to use the first record as data.
Have you used "Get Info" to see what your Mac thinks a .CSV file is?
"Is there a way to force open the "don't import first record" dialog box?"
I'm pretty sure that if you use a .txt suffix on the file it will do what you want.
I think this was just an anomoly. I think that FMP remembered this file name and assumed it would be handled the same way. I now get the dialog box about how to use the first row. Could be one of those bugs in FMP if the wind is blowing in the right direction you get this behavior. Anyway today I can't reproduce the problem. I'll consider this one closed.