I have heard this rumour (???) too. However, in my experience is this not an entirely new feature, as the RSPCA was and is always very reluctant to invest time, money and effort into so called pest birds, game birds, or complicated cases. I have had an encounter of this kind just recently, as I nearly made the mistake to help an ACO to catch an injured moorhen. The bird escaped, but I was close enough to identify this bird as one of our residents, who was known to be lame on one leg since years without being bothered to much. The ACO lady told me to let her know when the bird is back a the pond to be caught. She also said, that this bird will die anyway, it will die either in the wild or it will be put down through the RSPCA.
rook