So your recommendation to a (clearly) brand new pilot, is to expect to meet the POH numbers?
Once competent to fly, and flying in accordance with the POH, yes, expect to meet those numbers.
But..... with the warning against flying in an environment in which failing to achieve that performance would increase risk.
The POH does not come with two sets of performance values, one for new pilots, and one for skygods, The information presented is factored for "average skill". New pilots are encouraged to use those values. But, like anything, when you're new at it, give yourself some extra room....
If you apply maximum power very early in the takeoff, and achieve it, in a properly configured aircraft, you would probably have to apply effort to
not achieve the height at 50 feet value as presented in the charts. There's a bit of skill in it, but it's mostly just physics....
As an aside, but on the theme, the 172
does come with two sets of numbers for spins. The more restrictive "Utility" C of G limits for intentional spinning, are for average pilot skill. At the "normal" C of G limits a safe spin recovery is still possible, but it will probably require skills beyond that of a new pilot.