@5871b4b8 I would say no, depending on the original context. in some cases it could be equivalent, but your shortened form is slightly different. it implies that they had to have done X to do Y, while the other says if they were to have done Y then they would've had to have previously done X, without implying that they DID do X. its subtle, I admit, but different IMO 

 @24a86ece Yes! That's what I thought when I asked the question. I still feel like "must have" is an improvement, but I think Warren's intent was similar to what you meant in the second case, like a hypothetical scenario. The former case could be interpreted as deductive reasoning.

https://iv.nboeck.de/watch?v=zOM9GV_7MpU&t=3594 

 @5871b4b8 these forms of chains of could/should/would and had/have get into very complicated forms of subtle changes to the meaning. even though I instinctively knew the slight difference in implied meaning, I still struggled a bit in my attempt to make the comparison using other words. I'm glad it seems to have come through :)