This is a great point. It wasn't like every home had a thermometer in the oven and therefore they had to use different terminology and identifiers for indicating oven temperature. Similarly, this is why American recipes measure in volume vs weight, most homes didn't have scales, they had cups and spoons.

These were also "precise enough" for the era. Perhaps these lexical gaps form as more styles of cuisine become more common and other cooking methods are used.

I've noticed this with some Indian recipes. The instruction "to grind" specifically refers to using grinders, either mill or wet grinders, that just aren't common in the US and that can create some ambiguity in how finely to chop or grind something.