The unusual thing is when I first applied through AMEX (in 11/20), it listed my Shangri-La membership as being valid only until 11/21, with a note on needing to achieve the 10 stays before this date to continue maintaining status. So yes, 12 months when I had applied - but my situation was quite different to two of my friends who immediately had their status show up as valid until 31/12/2022. We all applied and were approved within the same week.
At the time it struck me as unusual that only I had to maintain a stay requirement to extend it beyond 12 months, but sometime between then and now, my app has updated my membership to the same expiry. I'm not quite sure what happened...
A bit unusual in my instance, so I'm not sure if this answers your question directly.