Why the Trello Card Attachment filename shown on card is not the same as when downloaded?

[PSi]

I'm just a Trello Board user/member/guest. I've tried to download all Card "Attachments" for my safekeeping. The filenames I see on Trello Cards Attachments — like "This is the file.pdf" actually downloads as "File_a.pdf" or similar. By comparing the files on my computer and the Attachments listed on Trello Card I can never be certain that I've actually downloaded all the attachements. Why the dispalyed filename is not the actual attachment's filename that gets downloaded?

[Tymek Zapała _Colorful Budget_]

@PSi 

Renaming your attachments in Trello just changes their title within the card, the original file name stays the same. So the names of downloaded attachments are always exactly like their names in the moment of upload.

[PSi]

I'm just a user/member/guest or something, not an administartor of the board!

My intention is not to rename or change anything on Trello Board/List/Card.

I am just copying the Attachment file from the Card into my own home computer for safekeeping and for reading when I'm offline.

I would just like to know why the name of the attachment file displayed on the Card is not the same the attachment file gets when I copy the attachment into my home computer.

This is extermily confusing, as I cannot compare the attachment filenames shown on card with the names of the files I have already copied on my computer for reading when I'm offline. I cannot be sure I have the correct file copied, or if the original file on Trello Card has been updated since I copied it.

What advantage there is to anyone in dispalying wrong attachement filenames on the Trello card?