Is it okay to make deliberate use of body diodes of MOSFETs?

Yes, body diodes can be deliberately used.

Diodes will be formed between drain and source, due to the structure of the MOSFETs. This is called body diodes or parasitic diodes. The N-channel MOSFET cross-section (Fig. 1.1) and equivalent circuit (Fig. 1.2) is as shown below. (Body diode is shown in red.)

Fig. 1.1 Cross-section
Fig. 1.1 Cross-section
Fig. 1.2 Equivalent circuit
Fig. 1.2 Equivalent circuit
Fig. 2 Example of asynchronous PWM control
Fig. 2 Example of asynchronous PWM control

The body diode can be used to recirculate the motor current when operating the motor. For example, the high side MOSFET of OUT1 will be turned ON (t1) and OFF (t2) during asynchronous PWM control as shown in Fig. 2. During OFF (t2) period, the recirculating current will flow through the body diode of low side MOSFET of OUT1.

Fig. 3 Example of synchronous PWM control
Fig. 3 Example of synchronous PWM control

Note that during synchronous PWM control, the low side MOSFET will turn ON during recirculation as shown in Fig. 3, t3. Generally, using MOSFET instead of body diode for recirculation is more efficient and can reduce heat generation.
Also, dead time (t2, t4) is implemented to avoid shoot-through current during synchronous PWM control, in which body diodes will be used for recirculation.

Fig. 4 Example of recirculation path (from rotation to coast)
Fig. 4 Example of recirculation path (from rotation to coast)

In most cases when setting the motor from rotation state to coast, all MOSFETs will be turned OFF. During which, the body diodes will be used to recirculate the motor current as shown in Fig. 4.

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