Inconsistent behavior setting axis title

[melikovk]

There is some confusing behavior when manually setting axis title.

Taking the "Bar Chart with Highlighted Segment" example as the starting point.
Replacing the last line with

(bars + highlight + rule).properties(width=600).configure_axisY(title='Wheat')

removes the Y title.

When any of the charts manually assigns the axis title, as in

y=alt.Y("wheat:Q", title="cucumbers")

then default titles from the other charts are ignored, while manually assigned titles are included.
In that case attempt to set the axis title on the LayerChart is ignored silently.

Thank you,
Kamran