That is about proper standby behavior, when initialized.
When uninitialized, you have 100mA (1 unit). But no motherboard actually cares and the polyfuse or overcurrent protector is rated for 500.
Laptops are a bit more picky, especially since a lot of cheap laptops only use 1 root hub for all ports. I'm not sure if they still do that for usb 3.0.
Some motherboards have an software option to keep (some of) the USB's powered. This doesn't count for the data pins, unless they have some SuperCharger technology.
When USB devices want to charge, they ask for the power units. As they should. When they are assigned the power units, and the pc turns off, most gadgets are able to keep charging.
If the device actively monitors the USB state, which they should, they stop charging and won't continue until the operating system is awake again. Unless they use less than 1 power unit, which they are guaranteed when uninitialized.
USB devices shall limit the power they consume from VBUS to one unit load or less until configured.
The LED's in the cable are allowed to take 100mA. Since a cable won't enumerate as a device.
As you'd understand, charging your smartphone with 100mA is going to take a long time.