[timr]

I agree it's not binary -- and the SARS CoV2 debate, in particular, became a theater of the absurd -- but the categorical distinction is not entirely crazy: some viruses are much more sensitive to drying out or exposure to the environment and simply cannot transmit efficiently in tiny aerosols.

Tons of work has gone into weaponizing smallpox, for example. It's a non-trivial thing, even though smallpox is technically already a virus that transmits via aerosol. Many viruses will exist in saliva, and will happily transmit through direct contact, but won't transmit well via the air (mononucleosis comes to mind).