These passport details have been required by certain countries for some time now. The US started the ball rolling and the aircraft were not able to leave until the information had been transmitted to the US immigration authorities, indeed I believe that there was the possibility that it would be returned straight back if this was not done. I assume that the reason was to enable the US to check all the passengers against their records in advance of arrival, which seems fair enough.
Then a number of other countries jumped on the bandwagon and I am not so sure that anyone bothers to check this information at their end!!
Whether it would be picked up or not if you used false details, I do not know, but I personally would not risk it.
I do not quite understand what the big problem is unless you have something to hide
