When creating a bar chart, setting your trace bar style to ‘horizontal’ appears to have no effect. The setting reverts to ‘vertical’ no matter what you do.
The easiest way to reproduce this is to create a new chart, add a bar chart trace, and then use the feature to add sample data to the chart. The graph will work as expected with the sample data (it produces a horizontal bar chart). Now add a new, third trace to the graph, go to the styling menu for that trace, and try and set the bars to ‘horizontal’. It will have no effect on the graph and instead keep reverting to vertical mode.