I'm posting this here since my original post as a bug was closed with an "expected behavior"-type reply.
As referred to by the discussion mentioned in the LSL portal documentation for llGetLinkPrimitiveParams() ( https://community.secondlife.com/forums/topic/486118-only-set-ambiance-on-prim_projector/?_gl=11wd89ez_ga_T7G7P6DCEC*MTcwNjU2MzkwNS4xLjEuMTcwNjU2MzkwNy41OC4wLjA.#comment-2446570 ) the call with PRIM_PROJECTOR currently triggers shouting on the DEBUG_CHANNEL about an unsupported parameter.
I understand that PRIM_PROJECTOR is considered, for now, as write only, but I see no valid reason why it could not be readable at all.
The current situation is inconsistent in my opinion. While I understand the potential problem with texture rights, I believe the behavior of this parameter should be consistent with that of PRIM_TEXTURE: if the texture is in the prim's inventory, return its name, else if the owner has full permissions over the object return its UUID. Otherwise return NULL_KEY.
This is important to be able to "copy" a user-set parameter from one object to another for example, I want to read the parameters and send them to another object.
Please make PRIM_PROJECTOR behave just like PRIM_TEXTURE in this regard, as described in the discussion. Thanks!