And yet there is an intermediate version. Which is that we can have an "observer" that is a moderately complex QM system where further post-observations are possible though difficult. And we can conduct experiments along that line and observe the growing difficulty of future interaction as systems get complex.

Unsurprisingly, these experiments with "partial collapse" produce exactly the predicted results of QM. And are exactly in line with, "And if the system gets more complicated still, collapse becomes irreversible." (Where "more complicated still" is very simple compared to ordinary macroscopic objects.)