I understand the GP comment as saying "First commercial fusion power station construction will start 2050-2060" is different from "Perpetual motion machine construction will start in 2050-2060" or "FTL spaceship construction will start in 2050-2060" for the very reasons you gave (among others).
You read the GP as saying something different from what you are saying, but I think you are actually both saying the same thing.
I understand the GP comment as saying "First commercial fusion power station construction will start 2050-2060" is different from "Perpetual motion machine construction will start in 2050-2060" or "FTL spaceship construction will start in 2050-2060" for the very reasons you gave (among others).
You read the GP as saying something different from what you are saying, but I think you are actually both saying the same thing.