The marked-up 1950 aerial photo shows that these bizarre puny on/off ramps were just a repurposed existing street. Surely this wasn't best practices for highway engineering even in 1950.
source: http://jpeg2000.eloquent-systems.com/toronto.html?image=ser12/s0012_fl1950_it0008f.jp2
Meanwhile, there's a huge parking lot on the other side of Bathurst that persists. That land could get put to good use with zero negative impacts for anybody.