Most of the time, people who have posted education issues was due to the following reasons:
1) combination of degrees to get to u.s. equivalency without labor cert. allowing it.
2) combination of work experience and degree to get to u.s. equivalency (generally, the other serivce centers would not approve unless it is specifically stated that work experience can be used in the labor cert.)
3) Major mismatch - ie., field of study on labor says comp. sci but person has major in math
4) What does field of study on labor have to do with the job. ie., field of study says chemistry but the job is in computer science. Therefore, how does a chemistry degree relate to a computer science position.
Recently, I received the full response to my appeal on the i-140. I was surprised to learn that the basis of the argument was two fold. First one was that since I had to go to high school until grade 13, that in itself is equivalent to first year u.s. bachelors. Therefore, the three year degree I had in canada combined with my grade 13 made my degree equivalent to u.s. bachelors. The second evaluation stated that I had a u.s. CPA and the entrance requirements for a u.s. cpa is the attainment of a bachelors degree and that work experience is not allowed to get to u.s. bachelors degree for the purpose of CPA. Therefore, since a bachelors degree is a requirement for the attainment of a CPA and I have a CPA then I have the equivalence of a u.s. bachelors.
The part about the entrance requirements for my CPA or in your case to your masters degree is what would be argued that you have obtained a u.s. bachelors degree.
Note: I have not seen one RFE or denial in the case of a person with three years degree and a masters where the masters was considered equivalent to a u.s. masters. That doesn't mean there hasn't been any but from reading the AAO decisions and other posters over the last year and a half, I haven't seen it as an issue.
The real expert on this is dazzling.