How to select a proper crystal oscillator and load capacitor for BNO055 IMU?
This is mis-leading.

Their "load capacitors" are actually in series (with gnd.) in the circuit loop so their "Equivalent"  Load Capacitance,(Ceq=1/2C) is one-half (1/2) of the C value. Then the IC input and trace capacitance to ground is summed to this Ceq to get the total or "Load Capacitance" the rating you will find on 32.768 kHz (or any ) Crystals.

So it seems they, Bosch are suggesting you choose a crystal rated for 12.5 pF  with 1.5pF allotted for Cinput + stray. This implies you put the parts close to the pins and do not use a ground plane under the traces which adds a few pF but depends on details.  (0.5pF/mm typ)

This is not  the only choice as 12,11,10 pF is also avail,

Other common choices are 7 pF, 9 pF, which may be useful for reducing dynamic load dissipation in micropower applications.