Don't know about the difference in speed, but it does explicit say it's the fastest way of converting something into a number, because it doesn't perform any other operations on the number.

Decided to put on the sherlock hat for this.

So our expressions return a string! And the unary plus operator (+) tries to convert, as you suspected, any operand into a number. It's actually the recommended way of converting something into a number ⚡️

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Arithmetic_Operators

Wow. The + operator in front of exactly the same expression fixed it.

I'm now very curious why this worked.