The lighting of shulker bullets is too bright in the Overworld compared to shulker bullets the End and the Nether. Attached screenshot has more detailed information.
Update 1.10.2, 16w43a & 1.14.4:
In the End, the light randomly can be too bright and have normal brightness.
Update 19w45b:
Not as bright as they used to be, but brighter than in the end. Also, shulker bullet brightness rendering in the End no longer seems to have any issues.
Can confirm for MC 1.12.1. This can be reproduced by using the following command.