Reproduction steps:
1. Create a new project
2. Open the Package Manager and select Built-in packages
3. Disable the Unity Web Request WWW package
4. Click "+" button > Add Package from git URL...
5. Enter "com.unity.vectorgraphics" and click Add
6. Observe the Console window

Expected result: Unity Web Request WWW is enabled and no errors appear
Actual result: compilation errors regarding missing namespace are printed

Reproducible with: 2.0.0-preview.13 (2019.4.24f1, 2020.3.3f1, 2021.1.2f1, 2021.2.0a12)

Full error messages:
1. Library\PackageCache\com.unity.vectorgraphics@2.0.0-preview.14\Runtime\SVGParser.cs(460,32): error CS1069: The type name 'WWW' could not be found in the namespace 'UnityEngine'. This type has been forwarded to assembly 'UnityEngine.UnityWebRequestWWWModule, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' Enable the built in package 'Unity Web Request WWW' in the Package Manager window to fix this error.

2. Library\PackageCache\com.unity.vectorgraphics@2.0.0-preview.14\Runtime\SVGParser.cs(460,46): error CS1069: The type name 'WWW' could not be found in the namespace 'UnityEngine'. This type has been forwarded to assembly 'UnityEngine.UnityWebRequestWWWModule, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null' Enable the built in package 'Unity Web Request WWW' in the Package Manager window to fix this error.