For example, this submission written in APL (Dyalog) claims to be 39 bytes. It is 39 characters, but in the TIO link provided in the post (which happens to be an older version that is two characters longer but that does not matter) it says it is 41 characters and 87 bytes. Why does the score count as [number of characters] bytes instead of 87 bytes?
This post is just one example I found but it seems to be prevalent. This doesn't seem fair to the non golf specific languages.