For #1, what is most likely happening is that they are trying to maximize the use of the pre-sales engineer's time. I can't tell you how many demos I gave as a sales engineer, but I can tell you that the opportunities that progressed past that demo are much less than 50%. After a while, sales engineers can even grow resentful of their BDR or AE for what they view as wasting their time. You could probably maximize your chances of getting a pre-sales engineer on the call to demo it by clearly stating your pain up front and emphasizing you have a rapidly approaching deadline to narrow your options down to a final 2 or 3.
I completely agree with you on the rest of your points. It can be hard to find sales reps that do the fundamentals well.