My idea is that perhaps the sheet was placed wrongly in the perforater, for want of a better word. As it seems some stamps are like that at the top and the bottom. Some are just the top , and then others just the base.
Bears more investigation.
To quote spooner.
"The thick plottens"
For those who are not aware, Spooner was a person who would muddle colloquilisms, putting them in the wrong order, such as "that is water under the dam" instead of over. apparently there are hundreds of them, as people have made up their own as well.
Still not convinced about the perfs. Yes some perfs are scissored off accidentaly or deliberately cut off by collectors.
But for stamps coming from different sources it would have to mean that collectors were gathered together at one time, and when some stamps have come from overseas, and interstate, that would not be possible.
Some I still maintain would have to have been done when being perforated by government authorities. The cutting is too perfect on some, and too numerous in being purchased from all sorts of places.