The manual states
The bin edges specified in xbins should correspond to bin edges
in the original histogram. If a bin edge in the new histogram is
in the middle of a bin in the original histogram, all entries in
the split bin in the original histogram will be transfered to the
lower of the two possible bins in the new histogram. This is
probably not what you want.
Is there no method available to rebin all points using new edges?
no this is not possible because in general the exact information on the coordinate position is lost when filling an histogram. So when rebinning with different bin edges it is not possible anymore to split correctly the entries in a bin.
It would be possible when you have an automatic binning enabled on the histogram and you have created a large enough buffer. In this case all the entry coordinate values are retained.
In this case it is easy to retrieve the entries from the histogram and re-fill a new histogram with different bins.
If you need I can send you an example macro doing this