The animation of the lock screen takes a little while, maybe half a second before showing any information.
It's disguised as a fade in animation. This is annoying because pressing the home button to check my phone's status when the screen is off goes to the lock screen and then takes extra time to load up things like the time, the top bar etc.
My phone isn't slow, I don't know why it's forced me onto this slow animating gimmick from my Android Oreo upgrade. Everything was instant before hand.
The simple process:
-> Click Home Button
-> Shows wallpaper instantly
-> Fades in all text/buttons.