No that wouldn't be true; remember Nintendo is in control of the OS. My speculation was that a Switch Pro SoC upgrade would be more than enough to run current Switch games' docked modes as its portable mode. This wouldn't require any developer intervention: Nintendo could just set a simple flag/trick at the OS level, and tell the Switch games that they are "running docked" while portable on Switch Pro. The games wouldn't know the difference.
Then, for developers that want to and newer games, they could add a third profile for running on Switch Pro docked that could take advantage of the extra power for 4K DLSS and maybe higher resolutions textures, higher anisotropic filtering level, etc.
Unless you are also an active Switch developer, I'm going to defer to MVG's knowledge of the situation.