Matrix access and insertion in RPN

[logicalorbit]

Hello I was wondering how accessing matrices in RPN mode works for the HP Prime. The manual states that given a matrix M to access column n simply input M(n), or for element m_ij M(i, j), however this only works for Textbook/Algebraic mode. Looking at the 50g documentation it states that in RPN mode one should input 'M(n)' (with the quotations), however this does not work either. It appears that one must place the value(s) to be used for the call onto the stack and then either use M(1) for one parameter, M(2) for two parameters (M(0) simply returns the matrix). Is this supposed to be the correct way? If so why is it not clearly documented either in the 50g documentation, which was from what I have read RPN through and through, or HP Prime documentation (though it doesn't bother documenting RPN beyong chapter two)? It should certainly be clarified that the parameter to () in RPN mode is not the matrix access index (or stack index to parameters) but argument count.

tl;dr Is 1 Enter 2 Enter M1(2) Enter the correct way to access the element M_12? Would storing the value 9 to M_12 then be 9 Enter 1 Enter 2 Enter M(2) Enter Sto->?