re: perspective
When Venus is this side of the sun, it's only 50 million km from the Earth; this means it has to also be very very close to the ecliptic plan at the same time (which it isn't, normally).
When Venus is on the other side of the sun, its distance is about 250 million km and because it's so far away, it can be a little more distant from the ecliptic plan, and still be within the sun's disk and therefore it happens more often; but I don't knowwhen last time it happened.
Raoul