If you need a deep technical analysis of its internal structure (e.g., unpacking with obbTool or comparing file hashes against the original), that would require access to a specific sample – but for security reasons, such analysis should only be done in a sandboxed environment.
Millions of Android users in developing nations still run devices with 8GB or 16GB of total storage. After the operating system and essential apps, only 2GB remains. A full GTA: SA OBB consumes all that space. A 150MB highly compressed version is the only option.
The mobile gaming landscape has changed drastically over the last decade. With the release of Grand Theft Auto: The Trilogy – The Definitive Edition on mobile platforms via Netflix Games, interest in the original, classic mobile ports of Grand Theft Auto: San Andreas has seen a resurgence. However, many users looking to install the original 2013 mobile port on older devices often search for specific file structures to save space.
Some files labeled "highly compressed" are actually "ripped" versions. Modders may delete certain files to lower the size permanently.
This creates a demand for a version. Users hope to find a file that has been shrunk from 2.6 GB down to perhaps 200 MB or 500 MB, making it easier to download and transfer.