It's a prototype. Never went into production. Lots of pictures online of prototypes used in marketing materials which had to be shot prior to the product being finalized. This is typical of any industry. My guess is this particular plug was designed to simplify the user experience by making it perfectly clear how the plug was to attach, attach with one knob, provide support on the bottom to keep it from being bent down and breaking the connector, as well as provide strain relief, cable guide, prevent it from being used on the printer ports, and limit accessories to those authorized by Apple as the connector would require a license from Apple to produce, as other connector configurations would not fit, and this plug would have been patentable. In the end, Apple probably convinced Jobs it was too expensive to manufacture, overkill, and would deter 3rd parties from making peripherals for the Mac. In the end, they did decide on limiting the ability to attach common connectors found on the market by making the case openings custom tailored to Apple's svelt uniform connector designs, so only products designed for the Mac could be used. Ultimately this was redesigned for the Plus, providing much more room for standard industry connectors.
I think it's a really smart design, but arguably doesn't look as nice as the final solution. Also, it's hard to say, but the inability to plug just anything into the back of the Mac, like the original Sstem software forcing the user to use the mouse by not providing keystroke alternatives, probably helped the Mac succeed as an easy to use computer, and ultimately led to its overall success.
