If you have ShortCharXX or any of the Classic Columns they will be automatically copied when someone marks a Quote Won or if they Convert a Quote to an Order. Built in deep in the Epicor Magic ™.
Your Quote + Order should literally remain identical. makes the flow btw them better. I am not sure if it does the same for UD Columns, havent paid attention – but there was a time if you make a column on the Order, you should make it on the Quote too - KISS.
Ive seen this behavior since atleast Epicor 9.702A.