By that reasoning, Yeager's X-1 was not rocket powered since it was launched from the bomb-bay of a flying B-29 prop plane.

And a hang glider isn't powered at all. It has no thrust.

It's kind of a tricky bit of language because a hang glider actually is human powered if you consider how its direction is changed and how it stays aloft. The human isn't just cargo sitting there doing nothing. Without the human "powering" the hang glider it wouldn't stay aloft if you simply pushed it off of a cliff. If you are specifically looking at thrust that is easier to talk about.

In general, I wouldn't call a hang glider human powered either even though a certain amount of human power output is responsible for its sustained flight.

This is in contrast to a craft with a non human power plant. Even in cases where the human is using some kind of power output to further assist the aircraft, the output of the power plant is several orders of magnitude larger than the human's output. Which in some cases may be simply moving a control mechanism.

And then there are what could be referred to as human "assisted" craft where the human power output is actually equal to or close to the output of the non human power plant.

I think the human assisted craft are more likely to be reasonably useful. We're just not suitable for the type of sustained power output that is required for fully human powered flight.