Although they may exhibit some influence on the sound in idle mode they it is not the same
as leaving a hardware unit in bypass mode.
The hardware that has circuitry, by it's
very nature, will still 'colour' the sound in bypass mode simply because of the circuit
path's influence on the signal running through it. In effect, the circuitry is still live
even in bypass mode.
With plugins I think you will find that 'bypass' is not
the same thing as algorithms are not designed to affect a sound till they are
However, using a plugin in default mode is not the same as bypass
mode and will still have parameter variances at default setup that will affect the signal.
Stretch That Note