A gray card or color checker can be useful for scanner calibration, but not in the same way as for camera shooting.

With a scanner, the light source is fixed and consistent, so you usually wouldn’t include a card in every scan. Instead, a suitable target can be used once to build a scanner color profile, which then becomes the default correction for that scanner/setup.

That said, profiling does not make color perfectly accurate. It usually improves overall accuracy by reducing larger color errors, but some smaller errors still remain. In practice, the benefit depends on how far off your current scans already are. If your scanner’s color looks reasonably neutral and consistent, the improvement may be modest.

So yes: a color target can make sense for creating a calibration profile for your scanner, especially if accuracy matters across a large batch. But if your scans already look good, it may not make a dramatic difference.