feeding koi

I am sure this has been talked to death, but I don't recall , in my few
months here, that this came up.
I just dug up some older issues of 'koiworld' and read a few articles, on
feeding.
one said you MUST soak feed given to koi(either sticks or the round stuff)
for 10 minutes, since their digestive system is such , that if they eat
DRY(er) stuff, it will take the water FROM their innards to help digest the
stuff. & also that they cannot/should not eat the flake stuff..
now what parts of this are true?
I have been feeding a mixture of flake,stick,round stuff, & other things
that sink(for variety) to my pond critters...goldfish & koi, for several
months........
am I doing something dangerous to the koi?
please give me your input on this. thanks.