Let me clarify. THERE IS NO DIFFERENCE If Bob Calls for an Insight check, or Maxperon asks for about body language. The DC is going to be the same.
That's much different.
I agree that the DC will be the same. The bonus to the roll might be different, though. You're far more likely to get some sort of circumstance bonus or advantage if you give the DM a good description of what you are doing and how, and what you are trying to accomplish.
Conversely, if you're too specific or describe in a way the DM doesn't think works, the DM might actually assign a penalty, or even automatically fail you, it cuts both ways.
Personally, I would never do that, I think player engagement should be rewarded.
But, I've seen enough DMs penalize a player for failing their "guess what the DM is thinking" roll to not discount it.
Ultimately, it comes down to communication. The DM has to be clear with the players as to how he wants things done, and the players have to be clear on their preferences as well.
There are lots of ways it can look. From letting me know they look for signs of deceit, like sweating, licking lips, not making eye contact, etc., to telling me that they guide the conversation back on subjects that get those sorts of reactions to learn the person they are talking to. Those sorts of descriptions can help considerably, including auto successes, depending on the NPC in question.
It's not really player knowledge so much as it's roleplaying the situation in more detail and depth. Given the iffyness of skills like insight, it will be hard to get an auto success, but not so hard to get a small bonus to the roll or perhaps advantage. It's not really a way to avoid failure. It just helps reduce the chances of failure.
An Insight check isn't about how a setting's people, organization, motivations and goals relate to each other, but how the DM wants to give players/PC's that information.I think about people, organizations, motivations and goals, how groups relate to each other, what's going on, etc.
I'm being a little facetious/snarky here, but I'm imagining the following conversation:
Player: "Can I tell if he's lying?"
DM: "How are you doing that?"
Player: "Do I see any tics or other revealing behaviors?"
DM: "Well, do you think he's lying?"
Player: "Yes."
DM: "Then, yes, you see him blink rapidly, he keeps fiddling nervously with his ring, and he seems to stammer."
You’re saying this would be the case at your table?Let me clarify. THERE IS NO DIFFERENCE If Bob Calls for an Insight check, or Maxperon asks for about body language. The DC is going to be the same.
An Insight check isn't about how a setting's people, organization, motivations and goals relate to each other, but how the DM wants to give players/PC's that information.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.