I posted yesterday that, based on the preseason games, Sage seems likely to stick with 343 and felt, like you, that it was sensible for him to do so.
My reservation is that the 343 system, at least as practiced by Palace, involves five defenders and two holding midfielders. That places a significant burden on the front three to carry the whole of the attacking threat. All teams rely on their forwards to attack of course, but we have one less attacker and one more defender than a team playing a 4231 system. We also rely on two full backs for width, and they can only get forward if we are on top. To be on top we need the forwards to carry threat regularly, often by themselves initially. If we are going to play with narrow no10s they they need to be able to get on the ball in tight spaces, keep it, dribble, play dangerous passes and shoot. In other words, they need all round quality.
In contrast, a limited player who has a couple of good strengths such as pace, crossing, or an eye for goal, can perhaps do better on the wing in a different system. It doesn't matter so much if they can't see a pass, or have hit and miss control. A lot of wingers are like that. It doesn't matter if you don't have much awareness of what is around you, the touchline orients you and simplifies your task. You don't need outstanding quality all the time, you can offset it by staying wide and running loads. Most of the time, if you get it slightly wrong then the opposing full back will just tackle you and put the ball out of play for a throw in. The attack doesn't die. Give it away in the no10 spot, on the other hand, and the opponent usually breaks away.
Johnson absolutely cannot play as a no10. Sarr sort of can but he tends to play more like a second striker. Nketiah can't play there. Pino showed flashes and seems able to find space inside, but lost the ball so very often that he did more harm than good. None of them seem suited to playing no10.
It doesn't matter who plays upfront out of Mateta, Larsen, or Nketiah if we can't create chances, and we won't create chances if we depend on average attacking players displaying a type and level of all round quality that they just don't have.
For me, as much as continuity makes sense, the 343 system that was perfect for Eze and Olise is poorly suited to our current squad.