The premise behind the cross-platform transfers was to make it as seamless as possible for inbound GO customers to continue their journeys Downtown, thus reducing strain on Union Station. I was skeptical of this idea since Day 1, as we know customers are reluctant to make transfers, even with potential travel time savings (why get up from your seat, transfer, and risk having to wait another 5 minutes for a train?). But now with cross-platform transfers being eliminated from the Ontario Line altogether, there are now even more questions surrounding the attractiveness of these transfers.
It's important to have an understanding of the demand here, because the sole reason we have an Exhibition Station is to relieve Union Station. If we don't understand how passengers will behave, we could waste hundreds of millions of dollars on a station that commuters will have little interest in using.