That's not what double dipping means.

In this case, I presume they're taxed on their continued employment and so they're still paying into the pension they're receiving benefits on? I don't see a problem if that's the case. They contributed to the pension with an agreed payment date and followed the process correctly. I can understand how you feel that it's unfair, but I really don't see a problem unless they stop paying into the pension or stop paying taxes on their continued employment.