I would agree that you've read the regs correctly. And as the FSDO says, each 141 school and syllabus is different. You could have two schools at the same airport with programs that lead to the same rating with different entry requirements and syllabuses. A MEL ATP add on to a helicopter rating may be be a program the FAA set the standards for but no 141 school saw the need to develop the program and get it approved.
As has been posted in several threads, if you at all think there is a chance you could be getting a FAA ME ATP in the next couple years, take the written test before 1 August. On that date a new set of regs comes into effect and there is a requirement to complete a training program just to sit the written. The program must include several hours of sim time so it's going to be in the thousands of dollars. If you pass the written before August, you'll have 24 months to pass the checkride.