You are attempting a ‘there are no changes that are beneficial, and any changes that are beneficial were “front-loaded’ defense.
It is either...
a) no gain of information is possible
or
b) gain of information is possible
The fact that you want to tack onto b) ‘but only if the information was “front-loaded’ is inconsequential.
It is either a) or b).
Obviously you just admitted to b) which makes your a) statement no longer “operable” as the Clinton White House used to say.
There is no gain of information. It is just a matter of taking advantage of the information that is already there. And as Dr. Sanford points out in his book Genetic Entropy, when we do see actual beneficial mutations that change the total amount of available information, they invariably result from information loss, not information gain.