We made the left/right system originally for a VN we made for 2-Buttons Jam at the end of 2018. That entry was the lengthily titled What Do You Do When You Ask Four People Out and They All Say Yes? Glad you liked the control scheme!
I think I liked it most because it reminds me of games I play on consoles. played a few with choices where you just press the directional buttons. It allows me to play with the keyboard over having to use a mouse, and means I don't have to put my cursor over the images at all, something I enjoy. Never occurred to me that one could do the same with a visual novel, but it's a nice touch.