No, the Boost Mulch does not make berries ripen faster in X/Y, it dries faster.
None of the mulches in Pokémon X and Y cause the berries to grow faster. The Boost mulch allows you to water it more often(by shortening the drying time) making it easier to get a higher yield. The rich mulch just adds 2 berries to the yield.
Rich Mulch increases final Berry harvest by two Berries.
Boost Mulch dries the soil quicker, allowing the player to water the plant more often and obtain a larger yield.
Neither mulches in the question(or in X/Y) make berries ripen quicker, the rich mulch gives you 2 more berries that require less work while the boost mulch allows you to water every 4 hours instead of every 24 hours meaning the extra berries gained depends on if you remember to water the berries.
Source: Bulbapedia
Source for 4 hours instead of 24 hours: Bulbapedia again