Yes, 'mass' and 'unit' nouns are alternatives terms for 'uncountable' and 'countable'. They are used in Britain, the US and elsewhere, and are - in some ways - clearer terms than 'countable' and 'uncountable'. They obviously come from maths/science, and if you think of 'rice' as a mass noun ( a pile of rice, for example) and 'a packet of rice' as a unit noun (three packets, for example), this actually makes a lot of sense.