There are safety arguments both for and against allowing RHS co-pilots to taxi the a/c when it's their handling sector. But, if it is considered safe and desirable (essential, actually) to allow them to handle critical flight-phases such as take-off and landing, it is illogical to forbid them to perform the lower-risk task of taxiing, subject to the usual considerations when manoeuvering on or off a crowded parking stand.
Allowing full role-reversal for handling, except following an emergency, is an important aspect of pilot development, and was the norm in respected British airlines even before I was a rookie. I suspect the same applies in the airlines of most Anglophone countries, and probably in the main European airlines, but I stand to be corrected.
To repeat a point I suggested flippantly in my first post, you cannot expect a pilot suddenly to become a taxiing expert on large a/c during the short period of a command course, the non-revenue part of which will be conducted in a simulator. There are already enough pressures to be faced in the line training, particularly if it involves a type change.