Interestingly it's only recently that scientists have been able to demonstrate that bubbles rising in ponds can charge up and produce micro-sparks, leading to ignition of marsh gas. This phenomenon has been widely reported for centuries as Will O' the Wisps, but at last has been fully explained.
Which would imply that aliens are so bad at flying (or their ships are so dreadfully unreliable) that it's amazing they get here at all!
Alternatively, if they have the same levels of accidents as civil aviation then there are millions of them.
Neither stacks up really in my mind.
However, UFO...
I think the only real disadvantage with cantis is how the post mount ones are excellent at first until the pad wears and the mechanical advantage weakens. Post mount v-brake pad holders solves it.
Much of the advantage to V-brakes is the re-thought pad design. It also saves all that faffy post...
Just to add, 531db was a very specific tube set from Reynolds. The forks were rather over-built, so in a front end crash the frame was almost invariably damaged. It was later replaced by 531ST and 531c.