MOSFET Rds(on) development
The automotive industry is not particularly known for seeking out best-available solutions, rather they are very much into cost minimization. If the solution saves a bit of money and does not noticeably affect the gas mileage EPA numbers or warranty claims they will likely go that way.
While there have been improvements in MOSFETs, there is a basic equation that for a given technology and voltage rating the Rds(on) is inversely proportional to the active area of the silicon consumed, which obviously affects the cost and maybe even the packaging.
I successfully replaced a bad power MOSFET in a Nissan crossover fan controller module with a significantly beefier one, but I did confirm that the gate charge was not too much higher than the original- the drive circuit was not available to analyze. YMMV. If I was making something to sell I would have done a lot more analysis and measurements.