Traditionally mirror lockup has been used for this purpose, but you're right, in many of the lower-spec models, mirror lockup is ONLY for cleaning.
The reason that the 2 second delay doesn't stick is that... for years, it stuck, and people would set it and then forget. Then there would be a complaint here or at Nikon about a broken camera... it happens all the time. So clearly they made it non-sticky in the near recent past.
_____ Brian... a bicoastal Nikonian and Team Member
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