What’s the point of eating collagen when you’re already eating protein powder? Why do you think your gut would process it differently from any other protein?
Collagen is made out of mainly 3 amino acids:(hydroxy)proline, lysine, and glycine. So in theory collagen powder is giving you very high levels of those specific amino acids which would help promote collagen formation. I can’t say I’m familiar with the literature and if there is any data behind that - but thats your reason
I've tried collagen powder before, because it's very easy to take since it easily dissolves in drinks (and I think actually improves them), and I think it made my hair and nails grow faster but didn't do much else.
As mentioned by the other buy, something like whey powder or meat will have a very different amino acid profile compared to collagen. Like fatty acids and carbohydrates, amino acids get lumped together as a group, but they all have very different effects in the body (including competition).
Most people don't need to care, but amino acid balance can sometimes be a significant factor to health issues because of all the interactions involved, especially if intake has been tilted by a particular way of eating. It's reasonable to balance out whey protein with collagen.
Honestly the topic is so convoluted that with my current grasp of if, I can't currently make a useful or broadly applicable statement beyond "some people find collagen or glycine supplementation beneficial for their X". Individual trial and error basically, much like neurotransmitter affecting medication.