Yeah, that's an odd title, I know.

So long as no levels of solar productivity are researched, it is possible to place panel entities belonging to higher research levels; bots will place these higher output entities instead of the base solar panel. ie Having a blueprint made in late-game, and placing it on a new save.

Instead of 60kW panels, you could get the ~500kw panels as soon as you unlock bots.

Behavior is present with just Solar Productivity (and Base + Space Age of course) present in the save. Researching literally any level of productivity solves the issue (any existing, over-outputting panels get reset to appropriate entities). Is it practical? Not really? But it was definitely noticeable while waiting for the first level to finish researching.