If the records were sealed and the child never knew they were supposed to have allegiance to the Russian government, the child wouldn’t have a sense of allegiance to what he/she never knew. Of course, if the records became unsealed, the person might then have dual loyalty and be conflicted, so the very act of finding out the true birth circumstances could change the equation.
"If it is known that the child..."
Difficult to challenge something, in this sense, that isn't there.
In such a case I believe that for an adopted child that child’s true/valid birth information would be necessary to be eligible for POTUSA. I also don’t believe that the parents of an adopted child can claim the child is of their ‘natural birth’. In other words such a child should early be vetted as to full citizenship from birth to remove any doubts, something that was not done for Obama.