blink-matching-paren doesn't blink

[Dennis Williamson]

When I do

bind -v

one of the settings I see is

set blink-matching-paren on

but I don't get any blinking when I type closing parentheses at the
command line.

If I do

bind 'set blink-matching-paren on'

or have

set blink-matching-paren on

in my ~/.inputrc

explicitly, then it works.

Why does this show as set, but not work until it's explicitly set?

Bash 4.0, Bash 4.1, Bash 3.2