yawningdog
The article you quote encourages quite the opposite -- in a nutshell, if you have an AI, why not use it to fly better?
The problem is that instrument flying on a docile trainer without an AI (whether it failed or you just ignore it) is relatively easy. The faster and more slippery the aircraft, the more difficult it becomes.
I think for me the answer to the original question depends on circumstances. Two hours of bumpy IMC without an AP is certainly
possible, but the concentration it requires and the toll it takes in fatigue gives you less mental capacity for the big picture, and thus increases the overall risk of the flight. It may remain within acceptable limits, or it may not. I can see circumstances in which I might well decline.