Many companies do the same thing. The employee isn’t fired they are just asked not to return for the 2 weeks. I’ve never heard of the employer not paying out the 2 weeks.

What's the difference between this and gardening leave? Does Amazon not pay for those two weeks or what?

Apart from whether Amazon are paying the two weeks notice that they morally owe, one obvious difference would be if your next employer asks have you ever been terminated from a previous position.

Who would want to be placed in the position of saying yes I was fired because I was suspected of being a security risk?

Does anyone ever answer this question truthfully? I generally assume not. The only way to verify this is through a back channel (AIUI corps generally won't disclose the reason due to libel liability), unless the employee really screwed up and didn't sign a separation agreement, which (again AIUI) you'd only decline if you plan on pursuing legal action against your employer.

And if you're already on a back channel, then you don't care about playing fair.

You can just say that you were terminated because your manager at Amazon was insecure and didn’t trust you to not fuck things up?

Well you can of course but interviewers often discount candidates that slag off their old employers on the grounds that they’ll be difficult to manage.