The size does not matter. It can be mounted universally with any size.
I had the exact same situation as you and ordered the mount at some risk anyway.
I was able to fix my Sonos Arc to my LG OLED B9 65" without any problems, although a wall mount already goes through the same holes. You simply have to fix the Arc to the TV with this bracket first and then mount the wall bracket on it again through the same holes. The installation is described in the Flexson operating instructions and is child's play, but we recommend that two people do it.