Well what I was driving at (and again, by this person's self-assessment) is that you wouldn't learn all the meta of a language like C++ in a couple of months. I do believe anyone who can code is capable of learning it eventually, but I have never seen someone ramp up on that language from an interpreted one quickly. Which is not to say it's a badge of honor to code C++, it just is what it is.
I think if you talk about the narrow scope of learning a language's syntax for greenfield projects, it might be true that people who know one language well can quickly learn any other language. But some languages force you to learn so much other "stuff" before you can be professionally productive in it, and I think there's some danger in just repeating that any good developer can pick up any language quickly.
My bottom line point: if I saw a developer who I knew to be very competent fail to quickly ramp up on a very different language in a professional setting, I probably wouldn't revise my assessment of them being "good."
I think if you talk about the narrow scope of learning a language's syntax for greenfield projects, it might be true that people who know one language well can quickly learn any other language. But some languages force you to learn so much other "stuff" before you can be professionally productive in it, and I think there's some danger in just repeating that any good developer can pick up any language quickly.
My bottom line point: if I saw a developer who I knew to be very competent fail to quickly ramp up on a very different language in a professional setting, I probably wouldn't revise my assessment of them being "good."