Your right the option has gone.
I did a google search and a fair number of people are saying iTunes works out the need for gapless playback automatically and 'it just works', Pink Floyd Dark Side of the Moon being the album people usually refer to for testing.
The gap added, would in theory only apply if you are shuffling tracks rather than playing in album track number order.
It seems that we find the same references.
But the same problem I'm finding is that the itunes encoder that is bug.
When I convert a song into a lossless format, WAV for example, it is the exact time of the cd.
When I convert to a format loss, AAC or MP3, it's a discrepancy of some milliseconds. What I'd be in lossless 1:22,333 in loss is 1:22,489