I think the term you're going for here is heterogeneous multi-processing/computing, not asymmetric multiprocessing:

https://en.wikipedia.org/wiki/ARM_big.LITTLE#Heterogeneous_m...

https://en.wikipedia.org/wiki/Heterogeneous_computing

It even lists big.LITTLE there as a typical example in the second article. big.LITTLE itself never had different ISAs as far as I could tell, just scheduling caveats that lead to efficiency tradeoffs, like the first article mentions.