So much time has been wasted on reproducible builds which could have better spent on securing more important parts of Debian. Practically minor changes like a build timestamp being different is not an issue.
You can content addressing without reproducible builds. You just have a canonical version, which typically is built by the application developer.
What is a win is that two independent parties can run the same build, and get the same binaries.
This is important because it removes trust from builders: anyone can verify their output.
It just so happens that unimportant things like build versions impede that.
This has been the status quo in Debian for a while now. You can build, and use diffoscope to audit the differences.
It's a stronger security property to have bit-for-bit reproducibilty, and it looks like Debian are ready to commit to it.
I had figured the cost would decrease in time as deterministic builds became the norm (i.e. build tools stop including build timestamps).
I agree that it might not have positive POI. Bit tricky for me to judge.