In real life, I don't know if the guy passing me on the street is a physicist, a serial killer, a hot dog vendor, or a Navy Seal. Clothing and physique give a little bit away, but for the most part, I have no idea who any given person is, or what they are capable of.
The concept of PCs knowing the difference between a goblin cutter, a goblin hexer, a goblin blackblade, a goblin archer, and a goblin sharpshooter is illogical. At best, one should know that one has a bow and another has a rod.
This fails to account for the fact that most people aren't trained in combat/adventuring.
I am a fencer (Epee specialty). From that alone (I'm nothing special as a fencer) I can identify the different sword types, the different combat techniques that go with them, etc. The way a fencer stands tells you a lot about their skill level, the cut of their gear says if they are wearing borrowed gear or not (so gives some compatence info) or if the gear is tailored they are an avid fencer (so expect the top draw of manuevers).
I have also learned a bit of judo and karate, so again I notice the way someone holds themselves, shifts their weight as they move.
Now if I was a trained fighter (like a soldier, or a true avid fencer/martial artist) I would expect this ability to even more honed. So I admit that knowing too much can seem OTT, but if you have studied goblin fighting techniques, then spotting the different types of combatant - and guessing a fair few of the moves they may have is that that tricky I would think.
Just think how quickly most people can sum up a problem at work after a few years - now assuem "work" is fighting/dealing with gribblies.
FOr info: Our DM allows a MKnowledge check to get vague destriptions of powers (Likes AoE, uses Cold damage and can dazes/slow) and it work pretty well.