Questions about BBB/BBG dtb names vs. content

[Tony Hain]

When I built 12 current the other day, I found some confusing dtb file
names. 
First there were identical files :
am335x-bone.dtb                 beaglebone.dtb
am335x-boneblack.dtb       beaglebone-black.dtb

But there was not a matching one for green. Is that intentional?
am335x-bonegreen.dtb

Then the content didn't match the names:
am335x-boneblack.dtb       --       
compatible = "ti,am335x-bone-black", "ti,am335x-bone", "ti,am33xx";

am335x-bonegreen.dtb        --        
compatible = "ti,am335x-bone-green", "ti,am335x-bone-black",
"ti,am335x-bone", "ti,am33xx";

Aren't the strings in the compatible line supposed to match the file names? 
Is there a reason there are identical files in the dtb path rather than a
link? 
Is the fdt_file=""  line required in loader.conf if the am335x file name
exists?

I have the BBB running with fdt_file="beaglebone-black.dtb", and the changes
to it for turning on uart1. Should I have made the changes to the am335x
file instead, or should I create the beaglebone-green.dtb file for the BBG?

Tony