It seems Technical Service Catalogue is often misunderstood to mean a catalogue of different services from those in the Business Service Catalogue. It's not. It is a different view of the same services. ITIL SD 4.1.4 sadly refers to "supporting services, shared services" within the TSC which I think contributes to the confusion, but diagram 4.3 makes it clear - the services are the same in both, just the perspective and detail differ because of the different audiences: internal and external.