It is not a bug, it is an improvement.
Way back when (standard DBA) the Voucher description is what was saved as the description in the GL Transaction file. Users asked for the ability to edit the line by line description so we enabled that capability but if you didn't edit it, the transaction line was saved with what was displayed on the screen, which happened to be the GL Account description. If you wanted the header description to repeat for each line, you have to retype it.
Now, the GL Description is shown long enough to confirm that you have the correct account but saving the GL Transaction with a description equal to the GL Account description is pretty worthless, you already know what account it is when looking at a Trial Balance. So you can edit the line by line description but if you do not change it, then it will be replaced by the Voucher Description from the header which is what will be saved in the GL Transaction records.