Equip before research or purchase

Been playing the flying cinderbloc Phantom FG.1 with aim-9D missiles as stock.
Just noticed that im RESEARCHING AIM-9Ds??? Any explaination as to why im having to research these when I have already got them???

Does it mean 9Ds as a pair on each pylon? thats stupid, why the hell u gotta research that. Theyre useless against an F16 or a 23 anyway its just a roadblock towards the other missiles.
Atleast update the description?

You figured it out yourself.

so when aam got added u couldn’t use them until research well more advance aam got added so they gave aircraft 2 aam stock to help with the grind the aam would be the weakest in the research