OK, i found it: reverse-region.  Pretty similar.
It doesn't allow writting to a different buffer than the current one.
The proposed command here allow that and save some consing.

Writing the result into another buffer sounds quite arbitrary.

Is it really such a common scenario that this function should do it? Those who needs to have the result in another buffer can easily add a few lines in the calling code to make it so.

Out of curiosity I had a look at the current implementation of `reverse-region' and found it quite complicated and hard to understand what it does.