bazel: a bit more docs on updating bazel-orfs

Signed-off-by: Øyvind Harboe <oyvind.harboe@zylin.com>

Author: oharboe

test/orfs/README.md

@@ -11,4 +11,8 @@ A set of ORFS integration tests that runs in a few minutes suitable for inclusio
 
 ## Updating ORFS and bazel-orfs
 
-`bazelisk run @bazel-orfs//:bump`, this will find the latest bazel-orfs and ORFS docker image and update MODULE.bazel and MODULE.bazel.lock.
+`bazelisk run @bazel-orfs//:bump`, will find the latest bazel-orfs and ORFS docker image and update MODULE.bazel and MODULE.bazel.lock.
+
+Note that this update is needed infrequently because the compability between ORFS and OpenROAD only needs to be considered for `bazelisk test/orfs/...` tests.
+
+bazel-orfs is updated at the same time as ORFS with the command above. bazel-orfs must sometimes be updated due to changes in the ORFS interface(such as variables.yaml updates or names of output files).