There are several cases in CPython sources when PyList_AsTuple() is used with just created list and immediately after that this list is Py_DECREFed. This operation can be performed more effectively since refcount of items is not changed. For example it gives such speed-up for BUILD_TUPLE_UNPACK:

Before:
$ python -m perf timeit -s "l = [None]*10**6" "(*l,)"
.....................
Mean +- std dev: 8.75 ms +- 0.10 ms

After:
$ python -m perf timeit -s "l = [None]*10**6" "(*l,)"
.....................
Mean +- std dev: 5.41 ms +- 0.07 ms