__Internal is only for linking extern methods with statically-linked native functions in Unity IL2CPP. If the intent is using the system-provide d libsqlite3, LibraryPath should be kept as sqlite3. However, if the Unity project integrates SQLite using static library or source code, then LibraryPath should be kept as __Internal . - source
For anyone trying to use Unity IL2CPP with CsvHelper, you need to add the following link.xml file to your Assets folder (can be in a subfolder).
<linker>
<assembly fullname="CsvHelper" preserve="all"/>
<assembly fullname="System.Core">
<type fullname="System.Linq.Expressions.Interpreter.LightLambda" preserve="all" />
</assembly>
</linker>
The link.xml file tells IL2CPP to not strip these particular assemblies - source