When you take this action, immediately take a “Build a Mine”
action. You get the shown number of free terraforming steps
to make a planet habitable. If you take the two-step action, but
need only one step, the second step is lost. You can pay ore for
additional terraforming steps, but you cannot combine this action
with another action.
Technically, it's a legal move. He wasted his power, but he probably used the QIC needed for the gaiaforming. (Can easily be checked in the advanced log).
I agree, maybe a warning would have prevented him from wasting the action.
