It seems like data wires that represent arrays, or at least specifically an array of class references, are treated as execution wires instead of data wires when it comes to wire thickness styling.
Hello ,
I was able to reproduce this issue on our end. I have written up a report and I have submitted it to the developers for further consideration. I have provided a link to the public tracker. Please feel free to use the link provided for future updates.
Link: Unreal Engine Issues and Bug Tracker (UE-50491)
Make it a great day