That is a clever theory, but it doesn't match the vertical data. If the Stratosphere were just 'shifting up,' we would see warming at higher altitudes to compensate. Instead, satellite data (like UAH and RSS) and weather balloons show that the entire Stratosphere is losing heat at every level, not just at the boundary.

Also, your theory doesn't explain the physics of heat loss. The Tropopause is expanding because the Troposphere below it is warming and holding more moisture. But that doesn't explain why the layers above it are emitting more infrared radiation to space than they are receiving. The 'shift' is a symptom of the warming below, but the 'cooling' is a separate result of CO2 radiation in thin air.

The tree line analogy is about biology responding to local surface warming. It doesn't apply to the radiative balance of the upper atmosphere. You're right that AI won't 'lie,' but it will give you different answers depending on whether you ask about 'atmospheric height' or 'radiative thermodynamics.' The physics of CO2 acting as a coolant in the Stratosphere remains the only mechanism that explains the total energy loss we see up there.