It just seems to be a common defect with these particular models. It is still well within warranty, by the way. He in the end simply refused to have the machine serviced. All it does is turn on the little light 'Sleep Light' I think, on the thing you press to release the latch. I was extremely disappointed by the service from that particular Genius. I have a MacBook Pro that was running 100 okay, until yesterday morning when I turned it off as I ran out the door and arrived home to a MacBook that will not turn on. This page will help you to locate the LCD display for your Apple MACBOOK PRO 15 device. He also kept calling it a dead pixel problem despite me many times explaining it was a reflective layer problem and that the Service Provider in Singapore was prepared to replace it (I even showed him the form). SELECT YOUR Apple MACBOOK PRO 15 MODEL: MACBOOK PRO 15 A1707 (LATE 2016), MACBOOK PRO 15 A1707 (MID 2017), MACBOOK PRO 15 A1990 (2019), MACBOOK PRO 15 A1990 (MID 2018), MACBOOK PRO 15 Retina Model A1398 (2012). We took the same machine to the Apple Store in Southampton (UK) and the Genius said that lame prepared speech about how you'd need "six of these spots for it to warrant a replacement".
Sadly the part didn't arrive in time for our departure. We did take my dad's one to an Apple Service Provider in Singapore (while we were on holiday) and they were prepared to replace the LCD. Genuine Apple part, pre-owned, with a 60 day warranty. I honestly can't say when these appeared as I may have simply not noticed them until recently. 24 inch Intel iMac, Early 2008, Mid 2007, 922-8469, LCD Glass Panel for 68. His one has a bright streak-like one on the left side of his screen, mine has a tiny one right at the bottom where the Dock is and a faint splodge on the far right. My dad and I both have the June 2007 model and both of them show the exact same kind of defects.