The main issue with calling them "Hybrid" is that they are not the first hybrids to be made by Xiaomi and 1MORE (an audio device company established by three former Foxconn executives thanks to the investment of Xiaomi):
http://www.xiaomitoday.com/premium-quality-xiaomi-headphones-launches-for-31/
The last paragraph states "The value for this is amazing, considering the next competitor, the Iron Ring Hi-Fi headsets cost way more than what this pair of headphones are currently priced at."
http://www.1more.com/en/acoustics_list.htm
That "1MORE Multi-Unit" is the first "Hybrid" by 1MORE, Iron Ring is the second (they are also made by 1MORE to be branded as Xiaomi).
You can see that some Pistons are under the 1MORE brand (while others were branded as Xiaomi, but made by 1MORE nonetheless, because Xiaomi doesn't make audio equipment themselves, 1MORE does that for them)
"Hybrid"/"Multi-Unit" on left, "Iron Ring" on right.
Another evidence:
http://www.1more.com/product/show-218.html
The text "1MORE多单元圈铁耳机" translates to "1MORE Multi-Unit Iron Ring Earphones". Saying that it's "1MORE Multi-Unit Hybrid Earphones" makes no sense. (Multi-Unit = Hybrid).
Conclusion:
Both earphones use the Hybrid dual-driver technology, both are called "Iron Ring", the first one is 1MORE Iron Ring, the other is Xiaomi Iron Ring.
Hope I made my point.
* It is entirely possible that "Xiaomi Piston Iron" is the correct translation, because "ring" may refer to a "piston ring", even though the word "piston" isn't in the original Chinese name. The source is this
official Xiaomi Czech store:
http://xiaomi-store.cz/cs/sluchatka-a-handsfree/119-xiaomi-piston-iron-6954176846044.html
* In Russia it's called just "Xiaomi Quantie":
http://store-xiaomi.ru/garnitura-xiaomi-quantie