See I would approach that differently - it's not that there are orcs in the hill but there are reports of ... and then go on whatever notes or ideas I had. Perhaps there are no orcs because there's a new version of troll, or maybe undead have been rising up at every night of the full moon killing everything including orcs, whatever I had in my notes. I don't make players guess the right thing to ask for, if they may have knowledge of the hills then a successful roll means they actually do have knowledge of what monsters are in the hills orcs or anything else. If I had nothing in my notes and I was uncertain, I'd roll to resolve that uncertainty or perhaps I'll throw in some orcs because I hadn't thought about it, it doesn't contradict existing lore and I can think of a way to use them. At the point I answer the question, the player has no idea how I came to the answer. They just know they have a decent idea of the hills.
There's nothing wrong with there being orcs or some other creature in the hills and I think at this scale it works just fine with D&D if that's what you want. But in general I'll already have a basic idea of what's going on, there's no reason to add quantum orcs that may or may not exist based on a player's roll. This is true especially because I tend to drop hints here and there, foreshadowing what may exist in them thar hills. If the player decides that, I'm limited in what I can foreshadow or link in to other existing plans.
Sure, I was just pointing out different approaches.
Your approach is in the traditional camp. The PC can FIND OUT if there are orcs in the hills; Through skill rolls, divination, actual investigation - whatever. But the PLAYER has no actual say as to whether the orcs are there or not.
That's generally the way it's done in D&D - certainly 5e.