This is not true at all. I have known dogs who developed a lifelong OCD due to the owners playing with them with laser lights or flashlights. IMO and IME it has little to do with rewarding or signaling them that the game is over. It has to do with these games making dogs notice things they generally never would have and give these things abnormal value to the dog such as reflections coming through the windows, shadows moving on the ground, light spots reflecting off of something shiny. I suspect most people who have spent much time around dogs with light/shadow chasing OCDs would not play with laser lights or flashlights with their dog.
There is absolutely no way to know when you began playing these sorts of games with your dog if they will or will not develop an OCD from it and by time you know, it is already too late to do anything about it. It's never really safe to play these sorts of games with your dog, even with rules and rewards they can cause problems. The unfortunate thing is that these games seem to be highly rewarding for humans. This makes it hard for even generally knowledgeable and caring owners to stop such play and encourages the justification that "Well X dog played these sorts of games and was fine" or "I play by certain rules, so my dog will never have those problems".
Some more information:
"It is strongly recommended that you do not use the laser pointer to play games with your dog. Nearly every dog will enjoy chasing the laser dot, but it is not worth the risk. There are safer games to play, and dogs who enjoy chasing laser dots will probably be just as happy to chase a ball or play tug."
Are Laser Pointers Safe for Your Puppy Dog?
"You see, I'm the owner of a Border Collie who has developed obsessive-compulsive disorder due to our innocent use of a laser pointer as a toy. After the first few times we used it, we noticed that he'd keep looking for it for almost an hour after it had been put away. After a few more uses, he started noticing shadows or reflections on the walls. Now he'll stare at the walls for hours and chase shadows—it's even really hard to tear him away to eat or go outside - it's an extremely sad condition!
A quick web search will reveal some technical information - apparently the laser sets off something in their brains, similar to as it might cause an epileptic seizure in some people. Once "switched," this is all but impossible to turn off, and one can only hope to ease the symptoms with deliberate therapy. That same web search will turn up even sadder stories about OCD dogs who have become insomniacs and worse, all because of laser pointers. Apparently it's the active, attentive breeds that are affected the most."
https://www.facebook.com/topic.php?uid=77978885595&topic=10812
http://www.showdogs.co.za/articles/wag_the_dog/qa19_shadow_chasing.htm
https://www.facebook.com/topic.php?uid=77978885595&topic=10812
And a Google search for "laser OCD dogs" or "laser canine compulsive disorder dogs" will reveal page after page after page of discussion on this subject.