I don't think bicycles on Stephen is an issue in itself.
I remember the cycletrack debate back in the early 2010s and some people freaked out at the concept of bicycle on Stephen being "added" when anyone with any regular experience there knew they have always been part of the street activity for decades. The way people talked about their concerns of bicycles being added was completely divorced from reality of where the real risks to pedestrians are in the city centre. Many failed to consider that no matter how busy Stephen is, no matter how many "no cycling" signs you put up, it's always a safer route than 9th and 6th to use, especially for less intense riders - exactly why it had bicycle traffic before the cycletracks and continues to today.
It's another one of those weird things we do to cater to car hegemony in the public realm. We spent a ton of energy and time debating the merits and minutiae of two modes - pedestrians and cyclists - sharing Stephen Ave, forgetting that we only are asking for this so we don't take any more space from vehicles. Vehicles obviously are the the actual dangerous mode in the inner city and they have the most surplus infrastructure that isn't needed that can be repurpsed. 9th Ave has spent decades as an overbuilt car sewer, antithetical to an urban condition literally right there. So if we want to talk about near misses for pedestrians on Stephen we should be removing all cars after 6pm as well given the amount of vehicle/person collisions I have seen over the years (not to mention every other intersection of our major downtown roads).
With all that said, I totally agree we need parallel cycling routes, likely one on 9th and 6th. That would be awesome! Wherever possible we should separate cyclist and pedestrian traffic formally. It would be great if they could close Stephen and still provide a reasonable and safe alternative route for cyclists to allow for full-street patios, events etc.
Of course, the merits for or against maintain a cycling route is not the real reason we would struggle to implement a full street patio. Vehicle/taxi circulation and delivery vehicle assumptions by businesses, planners and transportation engineers would be the actual barrier to implementing this.