listing image thumbnails position

I am new to amazon and preparing my first listing. I see some listings have their thumbnails on the left. while others on the bottom

Eg , this ones thumbnails are on the left https://www.amazon.com/AIEVE-Compatible-Sandwich-Chocolate-BPA-Free/dp/B0BG23797H/

this ones are on the bottom https://www.amazon.com/AIEVE-Kitchen-Appliance-Sliders-Compatible/dp/B08FLKF9SF/

what is the reason for this ? is this just random ? is it about mobile vs desktop optimized ?