Statue of the Unsung

[Hinoto-no-Ryuji]

But the shape remains the same, which is too similar to the shape of 6's horns.

Again, 6's horns aren't as close to the minion's as you think. The minion's sweep up and backward; 6's curve dramatically forward and backwards. Because 4 is an overheard view, a direct comparison is a bit difficult, but if I had to choose which dragon's horns more closely resemble the minion's, it'd be 4. The shape and orientation of 6's is just too different.

4 is literally covered in feathers, and 6 only looks like a bird because it's mouth is wide open. If anything, 4 is much more birdlike.

4 is covered in spiky, pointy scales. Really not sure how you're getting feathers from that. 6's neck is the one covered in feathers - which, when combined with the beak, is what we mean when we say it's bird-like.

4's wings also look like they have feathers on them.

I think those wings actually belong to 6 (that's just a guess; it's really hard to tell exactly whose they are, but the feathers on 6's neck make that seem likely to me). You can clearly identify 4's left wing, and it has no feathers at all.