The article you linked is in error — plain and simple. The top budget pick, for example, is claimed to have 0.7ms input lag and 1.0ms gray to gray response time, which is obviously wrong — how can total input lag possibly be less than the time it takes for pixels to physically change state?

So I looked the model up on rtings (who does their own objective measurements — a much more reputable source than some random blog post / sponsored link ad) and their tests show it’s not much different from the LG C9: https://www.rtings.com/monitor/reviews/asus/vg248qe

At best, the Asus VG248QE achieves 5.1ms input lag, with 2.1ms 80% transition response time.

At the same resolution (1440p) but lower refresh rate (120hz vs 144hz) the LG C9 achieves 6.6ms input lag, with 0.2ms 80% transition response time.

The LG input lag time you quoted is when running 4K at 60hz, which is a fantastic input lag for that mode, and as far as I know about as good as any 4K gaming monitor out there. The C9 is actually capable of variable refresh rate though at 4K via HDMI 2.1 as well, but no current video cards or drivers are yet capable of this — but when they are, the expectation is that the LG C9 will be a serious contender vs even many dedicated gaming monitors.

Be very careful when comparing specs between different sources, combining different measurement methods, or comparing input lag numbers when the displays are configured at different refresh rates and screen resolutions.