Anti-Shock is not the same as a fully electronic shutter. With electronic first curtain shutter (EFCS), the exposure starts electronically across the sensor, but it still ends with the normal mechanical rear curtain. Because of that, it does not have the usual rolling-shutter behavior of a fully electronic shutter, so the classic fast-subject skew issue is generally not the same concern.

It’s commonly used to reduce vibration, much like mirror lock-up on a DSLR, and can be especially helpful for macro or other vibration-sensitive shooting.

That said, it isn’t completely without downsides. Based on user experience reported here, Anti-Shock can produce banding in smooth areas like sky at certain shutter speeds (for example around 1/160s to 1/320s on an Olympus E-M5 Mark II). So while it avoids the main rolling-shutter issue of a full electronic shutter, it may still introduce artifacts in some situations.

There’s nothing here indicating reduced color bit depth or lower image quality as a general EFCS limitation. In short: Anti-Shock is usually beneficial, but watch for banding/artifacts at some shutter speeds and lighting conditions.