Windows' "split status"

[Chong Yidong]

IIUC the window-splits mechanism properly, it goes to a bit of trouble
to record the current value of `window-splits' in each window, when that
window is split off.  This recorded value is retrieved when the window
is resized or deleted.

Why?  Why not just refer to the `window-splits' variable?  Since
`window-splits' is a user option, I don't see any reason to regard it as
a "sticky" property of a window.  Even if the user happens to change the
value of `window-splits' midway through an Emacs session (which is a
corner case anyway), there's nothing wrong with simply handling existing
split windows using the new value, rather than whatever historical
values of `window-splits' they possess.