Hear a number of people, when hearing of someone who was killed tragically or conversely, someone who you have have expected to be maimed or killed, but luckily was not; say "It just wasn't their time." I have thought this was circular reasoning.

This is an example of unfalsifiability if really meant as an argument. However, in most cases, this is simply a platitude in an attempt to make someone feel better. It can also be an example of a tautology. If they die = it was their time. If they don't die = it wasn't their time.

It is just and expression. Maybe you can call it an opinion. Not aware that anyone uses that as a argument.