Sorry, I didn't mean that you personally needed to check, this might have worked when you made the video and posted it. I mean to anyone intending to grind out the achievement, please check early on to make sure you're getting credit by, like Skabais said, leaving the game and refreshing the achievement page. Better to figure out something is wrong 5 minutes into your grind session rather than an hour later.

I am sure ti still works but steam doesn't sync progress in real time, however it does sync after leaving game and refreshing achievement page.

Tutorial didn't work for me, had to use a different scenario. Strong recommendation: before settling in, make sure to test your method by doing a few deaths, then quit the game and check the achievement in steam (it tracks your progress, if it's counting it).