I get the whole number 1 / number 2 thing. Its been that way since the dawn of racing time however, it always seems odd that they treat car development as a zero sum game.
By helping driver A it hinders driver B. In the case of Red Bull, by shifting the development of the front end towards Verstappen's preference it reduces Perez's chances and therefore harms the team overall. What's stopping both sides of the garage doing their own thing? Why can't Max have his update and Perez keep his car how he likes it?
Many years ago it wasn't uncommon for drivers to opt for entirely different versions of a car to that used by their teammate.
No one would seriously consider Sergio to be a threat to Verstappen over a whole season regardless of their team status so it just seems pointless to not allow Perez to do his own thing.
Regarding the original point with Ferrari, its always massively awkward when the guy who is supposed to be your number one has so many issues. It makes favouring him look silly.