The 'someone' will have been working in the sorting office. Going back a few years, I rarely received mail with biro cancelled stamps, then the number increased considerably. I guessed that instructions had been issued for unfranked stamps to be biro cancelled when someone at RM HQ realised that unfranked stamps were being recycled but in my experience a few still escape being cancelled. I've had deliveries with stamps franked normally, biro franked and unfranked.
I heard that Ronsol lighter fluid will release the adhesive used on postage stamps without affecting the cutouts. I also heard of a few barcode stamps being recycled and going through the system without any issues.