As it stands, there is no obvious way to prevent automatic display blanking on the GNOME lock screen. There are several problems with this:

1. UX. I, for one, often lock the screen throughout the day, and expect it to always stay on. Desktop monitors may take a noticeable amount of time to wake up, which, in a manner of speaking, breaks the flow.

2. Risk of premature hardware failure. Frequent backlight cycling is unlikely to be good for a monitor in the long run, possibly shortening its lifespan, and (ultimately) contributing to e-waste.

3. Side effects. The last time I checked, waking up the monitor would cause issues with proprietary NVIDIA drivers, making fullscreen applications flicker, effectively rendering them unusable until a reboot.

As such, I believe that it should be configurable. Perhaps, a dedicated option could be added to the settings, or it could just inherit the global screen-blanking preference set by the user (e.g., "15 minutes" or "Never").