Histogram column is always showing "Yes" when viewing the columns of a table in the Columns tab of Schema Browser. However, this does not reflect the fact that some columns don't have histograms. For example, a table is analysed every night and having just added a new column all columns are shown as having a histogram except the newly added one.
The data dictionary SQL used by Toad is based on the density column of the view.
Waiting for fix in a future release of Toad for Oracle.