The investigation of technical solutions for a privacy-preserving contract tracing approaches in the context of the current COVID-19 pandemic shows that major differences and their perceptions in the field of data collection, data management, and data privacy exist. This is documented especially in the very recent report from the Republik "Die pragmatischen Puristen" (in German) as of June 26, 2020.
Interestingly, the CSG work on WeTrace, which did document, analyze, and discuss a Bluetooth-based, fully privacy-preserving tracing approach - all driven by the main idea provided by Alessandro De Carli, Papers AG, Switzerland, a former CSG Master student - resulted in the white paper "WeTrace - A Privacy-preserving Mobile COVID-19 Tracing Approach and Application" as of April 2020 and was referenced in the Republik report.
While the decision to keep a system - here an App - simple, is very well understood, the simplicity of a fully decentralized approach speaks for itself, too. Certainly, by adding security measures on top of Bluetooth, certain attacks can be prevented as well, but additional functions and code will lead to a more complex, thus, leading to a potentially less likely error-free approach. Therefore, WeTrace did propose a very basic, not complex, and secure mechanisms.
In any case, one general core conclusion can be drawn: research work under pressure of time will almost always pave the path to new and better results at later stages, especially when researchers are able "to read the book from the back" at any point in time later and when they will have more time to think about and experiment with further details new at hand.