For Olympus OM-D mirrorless bodies, one normal photo appears to count as one shutter actuation, not two. Community testing on an OM-D E-M5 showed that after taking a standard shot, both the shutter-press counter and shutter-actuation counter increased by 1.

Your original assumption is likely the issue: mirrorless cameras don’t necessarily need the same full mechanical sequence as a DSLR in live view. Many mirrorless designs use electronic first curtain or a mixed electronic/mechanical sequence, so they avoid an extra full mechanical cycle just to end live view.

That means the internal shutter count is generally the meaningful number for shutter wear/rating on OM-D cameras. Extra actuations beyond shutter presses can still happen in special modes or scenarios, but a standard single shot should not be counted as two.

So for an OM-D such as the E-M1 Mark III, the rated shutter life should be compared against the camera’s reported shutter actuation count, and that count should be reasonably accurate for normal use.