Hi @Cowtown_Boxer_Rescue and welcome to the Asana Forum 
Yes, it is correct; the attachment itself doesn’t live in Asana but in Google Drive; Asana only store a link to the document in Google Drive, so in order to make sure your colleagues can access you must grant them access to the doc via Google Drive.
While you can’t open and edit a Google Doc within Asana itself, you can still open it from Asana, which allows you to centralise your tasks with content you need to action.
Hope this helps! Pease let me know if you have any follow-up question! 