And ultimately, these devs speak code, which provides a common objective baseline for exchanging substance (which everyone certainly refers to if they can't decode their English). Their confidence likely stems for them objectively knowing how good their code is.
This is the case with science and mathematics, and with the bilingual students also. The best Japanese talent are all competitive at a global level. They aren't the issue. Them being rare is the issue. And though they should become assets to Japan, they quickly assimilate to the global community, at which point, the global community tends to appreciate and reward these people more. Many, if not most, end up in Silicon Valley or Hollywood or just working for a foreign company. Overachievers have a hard time in seniority based bureaucracies which most of Japan still is.
As marak830 commented here,
> I teach high school student part time (so I can work on my side project), and the
> teachers over the age of 40ish have pretty terrible English(these are English
> teachers), but all of the newer ones have pretty good levels.
That wouldn't be that big of a problem in a meritocracy. And it's going to be far worse with a modern skill like programming.
Compare with a hypothetical Japan where the program would not be put in place and all those people "merely" familiar with English were not at all. It'd be ridiculous to suppose such a plan would lead to 100% (or even 50%) of people being fluent.
> The goal is for fluency,
How many would have not been fluent were it not for the program?
> competency, and the capacity to be competitive at a global level.
Now many (and certainly much more than before) people will have both sufficient English comprehension and sufficient programming exposure to be able to read through foreign code, open issues in open source projects, and possibly even contribute back at some point, nurturing a virtuous feedback loop. Have you ever read core ruby devs? No offense meant but they're hardly "fluent" in English, yet they're able to exchange and contribute with the global community at large.
This is all about raising the bar and giving people more of a chance to stand in a global economy/ecosystem.