This "last update" of Lightroom-Classic-CC (v7.3) has now set Presets to automatically (and by default) show the effect of Presets on the main image window when the mouse cursor is hovered over the Preset name.
If you do not see the main image window change when you hover, then you do not have LR-Classic-(v7.3)
Some LR users are asking to turn this 'feature?' off, perhaps with a Preferences option box.