This is just a guess, but a splatter shield may be to prevent secondary emissions.
Amperex 6DJ8 tube construction
Here is a link to a picture of two Amperex 6DJ8 orange globes.
- The one on the left has a circular plate suspended between the grid and the O getter.
- The one on the right does not have the circular plate suspended between.
What does that circular plate do? Why is it not necessary in the other tube? Any other info? Thx!