Yeah, Robben has scored more than 10 league goals only once (for PSV in 2002-03) before moving to Bayern aged 25. He has then scored double figure league goals in 6 of the next 8 seasons (he failed to do that in two seasons when he has only played 15 and 16 league games respectively due to injuries). He has never scored more than 17 league goals though.
I don't think Robben is a good comparision though. I see Trincao as a playmaking winger which could be useful once Messi will leave and he could also move more in the centre. He has good football IQ and vision (still needs to improve his passing though) but I think he'd be the best utilised with an attacking FB making overlaps and playing 1-2s with him (granted it was against Andorra but he's done that quite well with Semedo from all people) AND by having a great scorer in front of him who he could pass to.
Yeah style wise Robben and Trincao are like night and day.
The comparison with Robben is that Robben became effective point wise later during his career. Could also take Mahrez who has a lethal left foot as well.
Somehow, even if Trincao has been underwhelming, he's had shooting opportunities during the games.
So at least he has some sort of talent of getting into good positions, maybe not the way Messi and Robben were doing it, but rather in his own way.