It's a cool picture, but I wouldn't look too deeply into it. It might bear a few superficial similarities, but I doubt Miura really planned the Falcon of Light that far ahead of time when he was just starting Berserk. As you even said, it's not a raptor, but a dove, and it's just a normal bird that Puck hitches a ride on as he's wont to do. At most, Miura might have gotten the idea to effectively recycle that particular imagery when it came time to draw the Falcon of Light.
If you wanted to attach some kind of symbolic meaning to that panel, I suppose you could say it represents how Puck is a small spark of light and innocence in the dark world that Guts is enveloped in.