In practical terms, what it means is that you can have your annual LPC on a Beta, Beta II or even HP and you'll be covered for all these R22 variants - but you'll need a separate type rating and LPC for an R44 and so on.
In other words, all variants of R22 are considered to be a single type. I think the term class refers to the situation where a number of less common types (Brantly 2B etc.) are grouped together, or for fixed wing (single engine etc.).