LTC4332 Vcc and VL at 3.3V but slave SPI device at 5V

Note that the Vcc and VL pins do not need to be the same voltage AND that the local/remote side Vcc or VL can also be different. 

Vcc powers the internal circuitry for the extender (including the transceiver) and would typically be connected to a supply which is able to provide the needed current for the part.

VL powers the external logic I/O circuitry which sets the logic level thresholds as a ratio of VL and has a very low supply current requirement since it only powers the logic I/O buffers.  

The LTC4332 will be fine if SPI bus pins are driven above VL as long as their ABSMAX of 6V is respected.   Thus your use case of 3.3V VL with a 5V SPI bus will not damage the LTC4332, but the noise margin for the digital logic will likely be reduced and this potentially could cause issues with the SPI communications under some operating conditions.  If you're going to do this, I'd encourage you review the logic levels to make sure you always have sufficient positive noise margin. 

Eric