Here's your proof of "soft" switches: Take two identical laptops. Make sure they're fully charged but don't turn them on. Remove the battery from one laptop and let them both sit unused for a couple weeks. Now replace the removed battery and boot up to compare power levels. The laptop with the battery left in will have less power, which would not be the case if "hard" switches were used. Hard switches completely disconnect the device from the power source, so there would be no difference in the power levels of these two laptops unless soft switches were used.
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So, some study into power draw might help:
1. All batteries do slowly seep power, even when not connected to anything. This is a tiny amount, but it's there.
2. A battery hooked up to a device will lose a little bit more power do to some components "leeching" a tiny bit of power after shutdown.
How much difference in power do you expect to see? It will likely be less than 5% between the two, which does not prove your experiment. A battery left attached to a unpowered laptop, a disconnected battery, or a "deep sleep" laptop will have negligible differences unless left along for an extreme length of time. "Deep sleep" modes on laptops may only consume slightly more power than a completely disconnected battery with the newest Ultra Book specs from Intel.
Window's Fast Boot does not affect the shutdown of a computer, merely the startup. Look into the power states of computers, which I believe range from S1 to S4 or some such. There are "deep sleep" modes that keep low amounts of power to RAM and CPU to allow for faster resuming of a session, but those are not forced on you by any means. Often times, you have to find convoluted steps in order to even activate these options.