Change in design on Shimano Ultegra 6703 crankset?
I ordered a middle chainring for my Shimano Ultegra 6703 crankset from Amazon. The chainring I got came in Shimano Ultegra packaging, but it didn't fit my Ultegra crankset. I looked closer at the chainring and it was engraved 'Shimano 105'. The chainring, really a chainwheel, had an inner section made to mount the inner chainring from. But on my Ultegra crank, the middle and small chainrings both mount directly to the crank. And the picture on the Amazon page looks like the chainwheel they sent me, and on-line forums refer to this middle chainwheel with the mounting for the inner chainring.
So my question is, what happened? Did Shimano change the design of their 6703 crankset recently? Mine is only a few years old. Or are there two different versions of the Ultegra crankset out there? And, even if there are, why was the chainwheel I got engraved 'Shimano 105' while the packaging referred to 'Shimano Ultegra'?