The left hand cable looks as if it is only just engaged in the lever compared to the right hand side. Is the lever sized on that side? Can you get someone to apply the handbrake while you look at the calipers? Also the difference in visible cable/ lever position looks as if there might be insufficient movement to engage the self adjuster to operate on the left side? If that is the case then the left brake might not engage as much as the right hand side. Is there a left-right difference in the MOT read-out?
Also, my MyY23 has less than desirable handbrake efficiency. Checked at dealer on two services and new cable fitted and readjusted at MMC. Slightly better but the MOT next year will be interesting! My calipers look different to yours. There is a return spring on the outside between the caliper body and lever. I did have a video of each side operating but deleted. I might do another.
The car is an auto so P park mode holds the car but not the ideal situation.ideal. On a hill stop I put the handbrake on then P mode if likely to be there a while. Short stop = footbrake only.

Plus Four MY23 Furka Rouge