What are the use cases of FIFO Half-Full and Three-Quarter Full interrupts in Receive FIFO of a UART?
If you know the exact length of the received message, then you should use an interrupt on received characters number.

The FIFO half-full, quarter,..-full interrupts are used whenever you recive a streaming data. Example: when it is half-full you process the received data (half) in the meantime the buffer shouldn't overrun. When you leave the ISR and do some other things the buffer is still filling, again you wait for interrupt when it is half full.

With bidirectional communication like master-slave, this kind of interrupts are useless.