You should not be surprised by that. As long as the “Change Order Amount” (or any field) exist in the REC variable - the system will compile as it is not a violation of the syntax to omit the REC in front of the field name.
What the system cannot decide is if the thing you are doing really makes sense [:D]
This is (even after more then ten years of programming in NAV) my favorite. It juste happened yesterday to me as well. I was setting a filter to one variable and in the repeat / until loop I summed up the field from a completely different variable. [:S]