How to reproduce:
1. Open the attached "1391542" project
2. Build the Asset Bundle (Build -> Build AssetBundles)
3. Open the "AssetBundles" folder found in the "Assets folder"

Expected result: Very similar or the same size of the files
Actual result: The file size gets incrementally raised

Reproducible with: 2019.1.0a2, 2019.4.34f1, 2020.3.26f1, 2021.2.8f1
Not reproducible with: 2018.4.36f1, 2019.1.0a1
Couldn't test with: 2022.1, 2022.2 ("Error building player because script class layout is incompatible between the editor and the player.")

Note:
- To confirm whether the size of the file was higher or lower sometimes deleting the file "assetbundletest" is required
- The increase in size usually happens after 3-4 iterations of the Unity Editor version, i.e: 20xx.x.5 -> 20xx.x.8