I don't see where it indicates anywhere that it's only about singles.
I think picking Dabrowski as the 'best performing Canadian' is the most logical pick, as she and Olmos have been playing great doubles on the red clay recently (won Madrid, lost in Rome final).
The pick makes perfect sense to me, as Gaby is pretty much the best doubles player in the world at this moment.
... And if Paul Rivard is considered an 'expert', the bar is pretty low.
In fact, with Andreescu's name appearing so often, I question the 'expertise' of all of them. Wishful thinking is all it is, as Bianca has barely played in the past 2 years, and, while she's done ok in her 'comeback', she hasn't exactly lit the tour on fire.
And, of course, with her there is always the possibility of an injury forcing her out of the tournament...