I can only confirm this works. Sort of.
In 2014-2015 I had an idea for a roguelike beat'em up game. Something like adding roguelike mechanics to Castle Crashers. I did google it, but there were no games like that on the market at the time, so I developed everything from scratch.
While developing I never checked Google again. And when I released the first version into Early Access in late 2016, I noticed that there are now two games in the same sub-genre that came out in the meantime. Apparently those were in development long before mine, but the developers didn't bother to tell anyone about it and they just hit the market (i.e. Steam release) one day.
Now, one of the games had a lot of ideas that I came up by myself. One of those was a magic potion called "Crank" based on the movie of same name. You have to keep moving and kill enemies or your health goes down. Exactly the same idea with the same name for the potion. I removed this feature from my game, because this other game was already out and I didn't want to be called a copycat.
But beside those few similar ideas, the rest of the development went completely separate ways. The other two games were mostly linear, mine has procedurally generated mazes to explore. The other two games allow you to carry and use one weapon, mine allows multiple. The other two games have a fixed boss at the end of each level, mine randomly picks one of 24 bosses, etc, etc.
In the end, I have built a successful product that is different enough to cater to slightly different market segment.
Had those two other games been on the market already when I started, I would have probably given up at the very start.
P.S. Sorry if my English isn't top-notch, I'm not a native speaker.