It is just older terminology Ron. I agree that it is wrong but it is much shorter than
“a substance that is allowed to flow into the middle of another”.
Perhaps “Gravity Injected” will do😁.
I just know that I have seen blueprints with a device such as you show marked as "injection device", a crucible, nozzle or what ever it may be.
I wish that I would have saved them--not, or remembered where I saw them---well--that is a trick that I have lost touch with..
As always---
Marble—On!!