In that particular part the BAW is part of a secondary, faster oscillator. It's leveraged for its spectral purity - its phase noise - rather than its accuracy. The datasheet you linked is for a clock chip that's designed to take in a reference clock and transform it into multiple end-use clocks.

A really neat thing you can do with that part is use a GPS receiver's pulse-per-second output as a high-accuracy, high-noise reference to generate high-accuracy, low-noise, high-frequency clocks. It's something you would see in datacenters or cell sites or distributed sensing systems.