Dara, you are all correct! The boys are making phenomenal progress, and yes, they probably are delayed when compared to a large population of baby boys of comparable age. The professional examinations made by the PT, OT and pedi aren't value judgements, they are developmental assessments. Nearly all preemies are caught up by age 2, but on the road to parity with their peers they may encounter bumps where they need additional support or even specific therapies. These kind of assessments, harsh as they may be to hear, are key to preventing problems down the line. With Lucy, the issue was speech development when she was 2-3 years of age. We could hear her issues with respect to enunciation, but the speech therapist was the one who showed us that she had already developed "holes" in her language development. She did nearly two years of therapy but one day the therapist called me to say that she was forced to graduate Lucy from the program because her testing now indicated that rather than being months behind as she had been before, she was now about a year ahead!!
You are the mom, so you rightly focus on their achievements and their potential... try and use the evaluations of the developmental specialists as tool to help them reach that.