Binding shift zoom does not work on second layered chart

[mrkbutty]

What happened?

I am attempting to bind the shift wheel zoom so that Y axis only zooms when shift is held.
The code below mostly works... zooming without shift only zooms the x axis.
Zooming with shift held will zoom the y axis only on the left, but the right side y2 remains static.

If I remove the "bind_y=False" and the zoom params from the following code then all three x, y, y2 zoom together.

Grateful for any help?

import altair as alt
import pandas as pd

df1=pd.DataFrame({'x':[1,2,3,4,5], 'y':[1,2,3,4,5]})
df2=pd.DataFrame({'x':[1,2,3,4,5], 'y2':[500,400,300,200,100]})

left = alt.Chart(df1).mark_line(point={'size':50}).encode(
    x = 'x',
    y = 'y',
).interactive(bind_y=False)

right = alt.Chart(df2).mark_line(point={'size':50, 'color':'red'}, color='red').encode(
    x = 'x',
    y = 'y2',
).interactive(bind_y=False)

chart = alt.layer(left, right).resolve_scale(y='independent')
xzoom = alt.selection_interval(encodings=['x'], bind="scales", zoom="wheel![!event.shiftKey]")
yzoom = alt.selection_interval(encodings=['y'], bind="scales", zoom="wheel![event.shiftKey]")
chart = chart.add_params(xzoom, yzoom)
chart

What would you like to happen instead?

I would like the y2 to zoom at the same rate as y, similar to normal zoom operation of x+y when not using the selection_interval params.

Which version of Altair are you using?

5.0.1