When you download Bitcoin Core today, the binary doesn't contain everything your node runs. It still loads the C library (glibc and friends) from your operating system which means there are version requirements, behavior that can vary from machine to machine, and code that your node executes that isn’t covered by reproducible builds.
New static test builds pack it all into one deterministic Bitcoin Core binary.
@fanquake is asking node runners to test out these new static binaries and report results.