The way C4D handles things seems to be pretty different from the way Max handles them. Well, Max is kind of industry standard now, if C4D had been there before it, things might be the other way round now ;)
Also, it seems to be hard to make use of the new viewport properties with external renderers, because of a poor documentation - no chance to blame the Corona team here (or the VrayforC4D one).
Being a former user of VrayforC4D (well, I still use 1.9 occasionally, but since I am stuck with R17 there, I use it less and less), I had more than one "discussion" with Stefan (Illab, the boss of the VrayforC4D team) about how things evolve with "our" version of Vray. It seems that devs have to "hack" into OpenGL as C4D uses it to improve the representation of models with "foreign" materials in the viewport (forgive my clumsy wording, I am not a coder, except for 3 or 4 line of Python I may have written ;))
Especially with material stacking, which is a dear and needed feature for me, I see some big issues coming to the Corona team. Stefan (also more than once ;)) explained to me that for making stacking work with polygon selections (which is essential workflow in C4D), C4D would have to suppord mapping per material channel. So, up to now, VrayforC4d still lacks this ability.
Please, Corona team, show your new "partners" how things are done properly ;)
All the best,
Michael