As a general rule, when a accDE is adopted, then almost ALWAYS then the data tables are separate.
This concept is a what we call a split database. What this means, is it is VERY unlikely that the accDE has the data. Since, if that was the case, then no changes could be made to the applcation, and then distributed to each user.
(since as you point out, any update to the software would also lose the existing data).
Think of any software development process. You tend to have two parts:
The application part.
That would be YOUR application, or maybe say word, or excel or whatever.
The data part
Those applications built (by you!!! - or maybe purchased commercial programs) are to THEN open or consume an existing data file.
So, you now have to put on your developers hat so to speak here.
So, now that YOU are going to develop software, then obviously this suggests that your software and data are now separate.
I mean, it would not make sense for example that if you obtained a new PDF viewer, then that all your PDF files would be gone, outdated, or overwritten then?
Same goes for using access as a software development tool.
What this means and suggests?
That the data in the accDE in fact DOES NOT exist!!! You need to look close, and find out if a corresponding data file exists.
So, in general, what a accDE suggests is that the user create a database file with JUST the tables. Then the accDB (and eventually the accDE) then use linked tables. In other words, the tables don't exist in that accDB file.
This setup in access land is what we call a split database.
You also don't note or mention is this data shared among users, or does each user have their own data, and such data is not shared among the users of that applcation? (this issue has to be first and foremost determined by you).
Now, it would be indeed strange that the accDE ALSO has the data file part. I suppose to upgrade such a users software, you would have to be given a copy of that accDE. Delete your tables in your accDB, import all the tables, and then compile back into a accDE.
So, be well aware that often a accDE will have what we call "linked tables". These linked tables will point to a accDB data file (or maybe even SQL server.
So, this is your first issue and challenge - you need to determine where and how the data is being used here.
As noted, it rather rare that a accDE will (or can) at accDE will have its own data, since as you point out, it would be difficult to update any such software, since the applcation program part, and the data file part are one and the same.
Knowledge of working with a so called split system is a basic skill set required by you, and this is especially the very instant that accDE's are to be adopted.
Here is a article and explain of this process:
split-an-access-database-3015ad18-a3a1-4e9c-a7f3-51b1d73498cc
Regards
Albert D. Kallal (Access MVP 2003-2017)
Edmonton, Alberta Canada