It sure does assign gg:

You can check it.
1. mossys:s/startup-sequence assigns sdk: if available
1. mossys:s/startup-sequence executes sdk:startup if available
2. sdk:startup does assign gg: sdk:gg

Note: this requires specific handling into the startup-sequence and only works with recent 2.x MorphOS versions. No chance with 1.x and early 2.x like 2.0, 2.1 and so on...