My baby koi I had in the basement pool were very shy at first, PL. They are smaller than the ones you bought. But, in time they figured out to come when I "called". I always talk to them when I go to the pool. Now, they come readily with the older koi, who were begging.
BUT, the goldfish I got from PondKid, never did feed or rarely, in the basement pool. I was worried as they started out not feeding in in the new pond. BUT, last weekend while I was working on the bog, right next to where they were, in time they figured out I was not going to "get" them, and started swimming nearer and nearer. It's just a matter of time and they will learn you are not a predator. Give them time, they will come around. Just be patient and stand quiet. I stand on my deck to feed the koi, so I'm far above them, and they have learned that's where the food comes from. So, it's not necessarily that getting low is the best, it's what they get used to. If you can toss food from your new deck, use that as your typical place to feed from. They will soon learn you are far enough away to not be a threat, but close enough to feed! Good luck!!!