REF: dont use compute_reduction
Full asv run shows no change.

This gets rid of one usage of libreduction.compute_reduction; #34909 gets rid of the other.
any perf impact? > any perf impact?

ran a full asv run and it said results were unchanged. @jbrockmendel this closed https://github.com/pandas-dev/pandas/issues/34506 ? > this closed #34506 ?

Looks like it addresses the example in the OP, not sure if it solves the general case.  Needs a test before closing the issue.