The gentleman does not know what he is talking about.
Normally it is ok to transport a refrigeration unit in any orientation. The problem arises when it arrives at its final destination. The refrigeration unit is designed to operate only in the upright position. This has to do with the way refrigerant and lubrication oils settle inside the unit when it is turned off. The system is designed to leak down after it is turned off, so that when the it starts again, the compressor can start easily due to the low pressure on the compressor side of the system. If the unit is started soon after righting it, or while it is on its side, refrigerant may build to high pressure levels immediately upon startup. This is a good way to burn out your compressor. In short, there is no issue with transporting it that way, but it is always recommended to let it sit upright for at least a day before attempting to start it.