Yep, not a scam, just bad shipping/stocking practices.
A lot of people may not know that in many industries (like the automotive manufacturing industry - my area of expertise) operate now on "just in time delivery" practices, which means they don't stock parts in a warehouse, the parts are delivered from a vendor on (ideally) the day they are needed. This isn't new, it's been going on for 20 years or so, but it's a big shift from the way things used to be where parts were held in stock in a warehouse on site until needed.
The point of this is that Optics Planet is attempting the same practices, and often failing miserably at it. I've noticed a number of other companies starting to do this in the gun industry as well; it saves them from paying for storage space for inventory, but overall it's a bad trend for us as consumers. If you have an opportunity to make your voice heard about this, it's worth stepping up and saying something. Places like Brownells and Midway who actually stock the parts they say they have deserve our business more than those making promises they can't back up, like Optics Planet.
I will say though that I've had good luck with Dvor, even though it's the sister company to OP. My success with them may be because I only ever buy their stuff when it's on sale, clearance, etc, which generally means they actually have it in stock and want to get rid of it.