100% is not the same as a mixture where you are relying on both fuels mixing properly.

Anything over 20% methanol and you cannot be sure the two fuels have properly mixed, which could result in a dangerous condition for the engine.

Plus of course the more you add, the more risk of damage to any unsuitable rubber parts etc within the system.
Staying below 20% should remain safe for a long time.

But obviously the fuel system in the car will need to cope with the extra flow demanded by mixing it with the petrol for any given power level

The biggest changes over the years though are largely down to modern turbochargers. They just keep getting better and better