I am aware of that model. It assumes there are only two variables present in the system. There are things called confounding variables.
If, for example, manufacturing capacity for EV's is limited by the supply of another critical metal such as cobalt, the demand for lithium will fall by reason of that constraint.
Or if two presidential candidates declare they are bringing EV manufacturing capability back to the USA, Chinese manufacturers would be cancelling forward orders, and running down their stocks.
After all, the US is their biggest market.
As I said, there is only enough lithium around for 30% replacement of EV's, unless it can be got out of seawater economically. IIRC, 55,000 litres of seawater is needed to produce 1 kg of lithium. The average EV needs 60 kg.
Thank you for the economics lesson, albeit unnecessary.