Yes—this can be normal. In SLRs, the mirror and shutter are mechanical parts, so tiny variations from inertia, friction, wear, tolerances, and lubrication can affect exactly how fast each part moves. Cameras are designed to be precise enough for photography, but not perfectly identical at a microscopic level.

Also, the video may be synchronized to the moment the shutter curtains start moving, not to the instant the shutter button was pressed. If so, one camera can appear to have a “late” mirror simply because its mirror-up phase took slightly longer before the shutter event used for syncing.

In practice, small differences like this usually don’t matter. Even an exposure that’s a little off from 1/2000s is typically far below what you’d notice in normal photography and within the kind of tolerance mechanical cameras have always had. If extreme timing precision is needed, that’s more the realm of specialized scientific equipment or modern electronic systems. This is also one reason mirrorless and electronic shutters reduce some variability from moving parts.