UVK5_BK4819_PROBE reassembles the sixteen bits a read clocks out and logs them against the register's own value: 1566 of 1566 agree on the working model. That agreement is not proof -- removing the skip_falling fix, which is exactly the historical left-shift regression, leaves the reassembled word unchanged, so this observation point is not the one the guest samples at. tools/test_bk4819_readback.sh therefore stays the guard.
tools/test_bk4819_readback.py is the working draft of a portable replacement (no source patch, no rebuild, no ARM gdb) and is deliberately NOT registered in run_tests.sh, so a proven guard is not swapped for an unproven one. Both the file and the two READMEs say so.
