Correct - but the effect is so large with shipments across continents that even 100+ year old car companies like BMW are doing quarterly inventory management:
Those 20-40% fluctuations in BMW's levels of sales correspond to quarter boundaries (!).
So I don't think Tesla has any chance but to do smart inventory management. You are right that it's not a genuine improvement of working capital - it's more like a robust quarterly
demonstration of working capital: it shows that there's no unhealthy growth in inventory, etc.
Tesla also renewed their efforts to improve delivery times in Q3 and Q4 - and that genuinely improves their working capital balance.