I wrote, paralysed leg engages more on COGY than on stationary bike.
It is probably because COGY is designed to make the most of our Central Pattern Generator (CPG). CPGs, which sounds like a small chip of computer parts, are actually systems we have in our body. Repetitive and unconscious movement such as chewing or walking are very much controlled by CPGs. The brain send signals to start, speed-up, stop etc, but once the movement starts, the movement keeps on without brain signal, with CPG circuits. we use the word "circuit" because one action works as a trigger to the next action. In walking, the movement of right leg leads to the movement of left leg, through the mechanism of CPG in spinal cord.
Image from https://musculoskeletalkey.com/the-human-central-pattern-generator-and-its-role-in-spinal-cord-injury-recovery/
In case of post-stroke, brain was damaged but not spinal cord where we have walking CPG. If we are set on the posture which encourages CPG activity, the paralysed leg will move, activated by the un-paralysed leg, without signals from brain.
Thus, paralysed leg engages much better than on stationery bike (and any other equipment).
There is also a report using EMG, proving the paralysed leg's engagement.