I agree this is standart advice also because OP situation seems not a player have experienced and confused, instead just haven't experienced yet enough.
I'm not against the different styles but TT is a spin game. I can't imagine a setup without any inverted rubber, also the game itself is designed for spin. Not have to but an individual should play with an inverted rubber, not only competing also for fully enjoying.
So the training time issue, as because majority of players are double inverted, I don't see this time a waste, you would get know your opponent, how the ball reacts etc. Also If we think, this player will play with at least one side inverted rubber, will have boarder arsenal.
Again, I'm not against the jpen + pips style, everyone is free to choose but I think it's not only disadvantaged also, missing out the Fun of TT. Otherwise it will be hardbat.
Additionally, as I remember, OP is complaining about jpen and pips for a quite time in the forum.