RangeToolLink turn background grey on one plot

[hoxbro]

I don't know if this is how it should behave, but I find it weird that RangeToolLink turn the background grey.

import holoviews as hv
from holoviews.plotting.links import RangeToolLink
hv.extension("bokeh")

c1 = hv.Curve([1, 1])
c2 = hv.Curve([1, 2])

c1 + c2

RangeToolLink(c1, c2)
c1 + c2

[droumis]

The grey is the currently selected x-span. Once you add a couple of opts, as in the example, you can drag the selected bounds.