Porsche kept a fleet of 918 prototypes as test bed and ongoing testing, so whatever improvement they found there it will be applied to customer cars. 

For the e-motors, shipping version of course will be tuned more conservatively for durability reasons, but with continuous testing, they found out they can push the motors harder without breaking it, so they upgrade the shipping cars. Plain and simple. Porsche don't really 'plan' upgrades, they just lump whatever they have on hand and release an update, and then whatever found next will be on the next one.


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