The following option doesn't seem to be working in the railcraft config.

anchors {

change to craftable=false to disable World Anchor crafting, they will still be available via Creative

B:craftable=false

I've set it in the config, and confirmed players can craft it. I've now set the config to remove all railcraft anchors but not tested it yet.
Using: Railcraft_1.7.10-9.5.0.0.jar from Infitech2 modpack by @JasonMcRay

Let me know if you need any testing.

Jason confirmed issue in the modpack.