Why is the Max CP of pokemon are all inaccurate
I feel like every website I visit including gamepress all the CP charts are all higher than what the pokemon actual true MAX CP at 100% IV. When you hit level 38 you are only able to hit the power up button ONCE after that the power up button disappears at level 39 and 40 you cant power up anymore. So what i'm saying is that there is no such thing as 38.5, 39, 39.5, and 40 to power up pokemon. My 100% IV Dragonite maxes out at 3530CP I'm currently at Trainer level 39 when I level to 40 my Dragonites CP will still be the same at 3530. This website Dragonites max CP is 3581 it just looks like that your chart ends at level 39 but really its 38 in the game.

Answers
@Sebhes Right I know what you mean I actually have a friend that did the double or triple power up glitch trick before Niantic fixed that bug problem.and he's 100% IV Dragonite is maxed out at 3556 CP.. But i pretty much got my answered covered when looking at the CP charts the actual true max cp you can get is at lvl 39 on the gamepress website 39.5 and 40 do not exist (unless you did the double power up glitch trick before Niantic fixed that bug)
Reportedly the game servers will take power up inputs up to level 40, but there is a client-side bug that removes the power up button when the pokemon reaches level 39.
People have said that if they raise a pokemon to level 38.5, then log in on two extra devices putting all three on the pokemon's page, they can press the power up button once on each of the three devices to get the pokemon all the way to level 40.
I am only level 34, and it was several months ago that I last read about people doing this, so I don't know if it still holds true.