Correct, see my post on this issue a few days ago. Probably should have said "tab name" instead of "abbreviation".
So it is NOT true that just copy-ING a bblx resource to the e-Sword directory will always get it to appear in one of the e-Sword resource tabs.
I will also point out that if 2 resources have the same filename, only one will appear. For example, if you have 2 bibles with the "Coverdale" abbreviation, only one will show in your e-Sword tabs. That could be an issue here as well for you.
Scribe has the longer answer. Some of what Scribe said needs to find it's way into the e-Sword User's Guide. I knew there was something I forgot...