A lot of gas stations have differently-sized nozzles for regular gasoline and diesel, and the fueling opening in the car is sized so that a diesel nozzle does not fit in a gasoline car. They should do something similar for e-fuel so people don't "accidentally" fuel them with classical fuel.

What you are forgetting is that diesel engines only work with diesel and gasoline ones only work with gasoline. This creates a natural incentive for the customers to not mix this up.

In the e-fuel vs trad-fuel story you do not have that incentive.

What you DO have, is an incentive to actually do the switch. Projections put e-fuel production costs at a 1500% premium over fossil fuels and wide spread availability is actually a hard scientific problem as even the announced global production capacity* of e-fuels is only enough for a few thousand vehicles.

* Apparently, to date, the biggest portion of announced e-fuel production misses either an energy provider or financial backing or both.

A good German summary: https://www.youtube.com/watch?v=MnrudYCzh2E