@Troy_is_gey I think you're right that the EA App is detecting that the other account doesn't own those packs and removing them. There's no fix for this, at least at this point. The only workaround I know of is to have two separate Sims 4 installs, renaming one "The Sims 4" folder at a time so Steam and the EA App only see one installed copy at any given time. The App won't detect the game if its folder is renamed.
This is not an official workaround and I can't promise it won't cause problems. But you might prefer it to the alternative of reinstalling your content every time.
To be clear, this is about the folder that contains the game's program files, stored here by default in EA App and Steam installs, respectively:
C:\Program Files\EA Games\The Sims 4
C:\Program Files (x86)\Steam\steamapps\common\The Sims 4
The folder in your screenshot contains Sims Delivery Express data and is not related to any of the above. The Sims 4 folder it's sitting in contains only user data, not program files.
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