It allows you to focus on features and pivoting over ceremony (boilerplatey / architecture stuff) and when you finally start hitting those performance limits, you have a luxury problem.
It will also be more apparent where to invest time spent scaling your product, whereas if you try to optimize out of the gate, you may still hit unforeseen performance issues.
This always sounds nice, but I've found that ceremony almost never really reduces productivity by much. The real wins/losses almost never have to do with ceremony related features of language, but rather architectural and framework components.
You build something that evolves by bringing in the smallest architecture and least fx components and then build. The language you use may dictate the fx components to some extent -- otherwise it's typically just to make developers feel happy (which is important, but really is just about morale more than anything truly inherent in the productivity of the language).
I was arguing in favor of 'growing something' as opposed to 'designing something' with regards to a hopefully growing userbase.
Language choice may be of lesser importance as you say, but I do feel that some languages fit the growing strategy better while others have a more design up front feel to them.