When using feet and inches, its fine to use precision of 1 inch as it's much smaller unit than 0.1 m.
If one says that they are 5'11" (180.34 cm), they can be 5'10.5" (179.07 cm) to 5'11.5" (181.61 cm) tall. That's 1.4% variance.
If using meters with one decimal place, and say they are 1.8 m (5'10.9"), they can be 175 cm (5'8.9") to 185 cm (6'0.8") tall. That's 5.6% variance.
Thus it's not really viable to use only one decimal place when using metres as unit, so in many languages it's easier to just say the length in centimeters compared to use two deeimal places.
What do you mean that blocking sudden noise in technically very challenging? I might be wrong, but from what I have gathered is that ANC is based on playing a "negative" of a pressure wave picked by the microphones in phase with the original wave. Thus it has to react to all sounds in the time that the pressure wave travels from the microphone to the ear, so it shouldn't matter whether the noise is constant (airplane) or sudden (gunshot).
Of course if the headphones have some kind of pass-through active, then it might take a while until software decides to activate ANC, but that is not a limitation of ANC itself