Focus is an accessibility parameter that can be used together with almost all other states in the states property.
Hence by providing it as a separate boolean property applied on the layer, it would have the following benefits
~ 50% reduction in the number of variants that would otherwise have to be defined. (Because almost all variants except few like hover states can be combined with the focus state)
Designers have more control on when and where to use focus state on components
Reduced impact on storage and memory with lesser variants, easier to maintain
Focus is an accessibility parameter that can be used together with almost all other states in the states property. Hence by providing it as a separate boolean property applied on the layer, it would have the following benefits