Except that in HFT we don't generally disable RTTI or exceptions. I work at a top HFT firm, have friends/colleagues at other top firms, have seen multiple people like Carl Cook at Optiver state in talks that they use exceptions... So what on Earth are you talking about?

Not using some or most of the standard library is precisely not an example of subsetting C++. Just because the C++ standard library has a hash table available doesn't mean that every project has to use it. Companies standardizing their own high performance data structures where it makes sense, and other things as well, is just something that happens and often makes sense independent of language.