The fact that the C++ committee is technically a subgroup of a subgroup of a subgroup is among the least of the issues of ISO for standardization.

The main problem is that ISO is a net negative value-add for standardization. At one point, the ISO editor came back and said "you need to change the standard because you used periods instead of commas for the decimal point, a violation of ISO rules." Small wonder there's muttering about taking C and C++ out of ISO.

I would argue that the structural problem is an underlying cause. So it won't be the proximate cause, but when you dig deeper, when you keep asking like a five year old, "But why?" the answer is ultimately ISO's structure and nothing to do with Bjarne's language in particular.

Hence the concern for the non-language but still deeply technical RISC-V standardization.