Besides, he created a prototype build and flashed it on a device with our base libraries re-implemented in C++, and the performance was about 20% worse. Hardly a compelling argument for C++. And these libraries were designed by a guy with like 15 years of industry experience with C++ working for tons of prestigious tech companies.
That's not to say that C++ is "slow", but it's certainly a bit slower than C, so if we could notice a performance difference on a device with 64 MB of RAM, I can't imagine how you could use it on a device with 16 KB of RAM. Even back in 2007-2008 our SoCs were probably several orders of magnitude more capable than a MSP430, being designed for flagship smartphones and all.