Yes—the warning still applies even when the camera is off. On lenses that do not support full-time manual focus, turning the focus ring while the lens is set to AF can force the autofocus drive mechanism, which may stress gears or the focus coupling.

The safe approach is simple: switch the lens to MF first, then adjust focus or retract it, and switch back to AF if you want afterward. That disconnects the autofocus drive so the focus ring can move the optics normally.

If a camera/lens system uses a body-driven AF motor, forcing the ring in AF can also back-drive the motor/coupling. On bodies without an in-body AF motor, the exact mechanism differs, but the practical advice is the same: don’t manually turn the focus ring in AF unless the lens explicitly supports full-time manual override.

So, being careful is not paranoia. Occasional forcing may not instantly break anything, but it does risk unnecessary wear or damage. Use MF before manually shortening or focusing the lens.