Considering these statements from devs, I’m fine with actual wording, even if it is a big simplification.
Imho this game has to attract ‘the masses’ and not only ‘aviation nerds’, like we mostly are. 
On the long run, devs need to gain reasonable profits, to be able to create a sequel or another great game. 
That’s not possible with a ‘nerdy niche product’… (I know, I’m painting black’n’white…)
Imho “small/medium/large” is perfect for anyone, who doesn’t know much about aviation - not yet talking about translating these more complex terms into other languages… 
Just my 2cents…