How is this confusing?
If it takes you 2 weeks with language X to write a sloppily written app, that works 99% of the time but has some errors -- and 2 months with Rust to write a version of the same app that has no errors, what you'd you prefer?
Ever heard of "time to market"? What good it would be if you get it 100% right, and your competitor has their app already out, and captured all your potential customers?
And even if time to market is not involved, would you really care for some occasional errors, if you get the majority of the functionality you want working just fine?
If you build pacemakers and airplanes, the answer is yes.
If you build regular websites, apps, and scripts, the answer might very well be no.
That's the case, just the numbers (2 weeks, 100% etc) are made up.