There are definitely requirements to monitor these types of spaces. Depending on the publication, guidance, or regulation you are reading, the particular publication may not specify whether two probes are needed.
Often the guidance is intended for locations that may not be temperature controlled. In my experience, only one monitoring probe is used for uprights and smaller, and the logistics of the use of the small space often makes it unreasonable to place a probe in the actual hot or cold spot. Instead a monitoring probe is placed in a sensible reference location, or the user simply standardizes their probe locations to a single type of location, such as just inside the door.
If your space is large enough to walk into the use of multiple probes becomes possible, but isn't necessary unless there is a significant temperature differential across the unit. For larger spaces, such as warehouses, multiple probes will be expected just given the size of the space, and you may find it useful to place probes in the actual hot and cold spots.