I don't think so? That PDF I linked is from 2015, way before Apple put focus on it through their M-series chips... And the Wikipedia article on "Glossary of computer graphics" has had an entry for unified memory since 2016: https://en.wikipedia.org/w/index.php?title=Glossary_of_compu...

For Apple to have come up with using the term "unified memory" to describe this kind of architecture, they would've needed to come up with it at least before 2016, meaning A9 chip or earlier. I have paid some attention to Apple's SoC launches through the years and can't recall them touting it as a feature in marketing materials before the M1. Do you have something which shows them using the term before 2016?

To be clear, it wouldn't surprise me if it has been used by others before Intel did in 2015 as well, but it's a starting point: if Apple hasn't used the term before then, we know for sure that they didn't come up with it, while if Apple did use it to describe A9 or earlier, we'll have to go digging for older documents to determine whether Apple came up with it

There are actual differences but they're mostly up to the drivers. "Shared" memory typically means it's the same DRAM but part of it is carved out and can only be used by the GPU. "Unified" means the GPU/CPU can freely allocate individual pages as needed.