If my memor yserves me right, it was renamed to D40 when AHII was launched. HT said that it was always D40 just named wrong in the game.
To answer the OP, I guess HTC thought that since most D30s were upgraded in the field to D40 standards, and they model only factory specs, the D40 is the more representative of "in service" late D model. On the other hand, our razorback is very un-representative. It has the water injection but not the paddle blade prop, so it is not really a very early jug, nor is it a "typical" razor back that were upgraded with both - these are the best jug fighters.