The strange part of it is that this was in response to a game that I've had for a couple of years. This was one of those typical jewel games where you flip the positions of coloured stones to create rows or columns of the same colour in a race against the clock.
The game has always been an ad-supported, but I've avoided installing ad-blockers on my phone because I can tolerate a few ads to support developers. Originally the ads were pretty unobtrusive, consisting of a small banner at the bottom, and the occasional full-screen ad after clearing a few levels. Over time, the ads became more frequent - usually after clearing 2-3 levels. For a brief span they had ads that would automatically bounce you to the download page for one of their other apps on the Play store, and I came close to dumping the game there, but they reverted that quickly after user complaints.
I did not play the game very often - and usually when I played, it was on long plane trips where I did not have net access, so their ad service behaved itself. Even so, whenever I played the game more recently, I noticed that it was up to popping an ad between every level clear, and then interrupting game-play to display full-screen ads. Again, after users pushed back, they scaled it back to ads ever 2-3 levels, and stopped interrupting in the middle of a level clear.
Today their game hijacked my lock screen with an ad. My phone had got an OS update earlier in the day, and at first I thought that Google had finally gone off the deep end. I closed the ad, and moments later it appeared again. I quickly realized it was tied to the Jewels Star, and I jumped to the play store to see if there were any comments. Sure enough, there was a flood of 1-star reviews by angry people who had encountered the same shenanigans.
The really insulting thing about it is that the developers are responding to the reviewers with a boilerplate response:
"ITREEGAMER June 26, 2017
Hello dear customer, thanks for your feedback and sorry for causing you this problem. We designed this lock-screen in order to make your screen more beautiful and protect your battery while charging. You can close it any time by pressing the button on the top-right corner of the lock screen."
The developers know that they have stepped over a line with this move, but based on their responses, they don't appear to care. I have a niggling suspicion that the company that developed this game may have changed hands at some point, because in spite of their irritating ads earlier, they were at least moderately responsive to the user comments. Now they are nudging the line between irritating and outright malware.
I'd recommend avoiding anything produced by these developers.