The first digit chooses which triplet, the second is the location
within the triplet. In the above example R02 means that I'm in
the 0'th triplet (which is the first one) and the second place in
that triplet. This is the 2nd row.

:22 means that along that row I go to the last triplet (2 of
0,1,2)
and in it to the middle square in the triplet (1 of 0,1,2).

Sudoku = the objective is to fill a grid with digits so that each column, each row, and each of the contained subgrids contain all of the "base's" digits.

Is this more of a way of referencing a standard Sudoku with base three?