Re: Negative Reps
I agree that beginners, well true beginners, don't have weaknesses cause they don't have any strong points, however, they still can be benefited from assistance work if they have imbalances, which would help them get stronger by being more well rounded (powerlifters often use rows to offset all the bench training, though it is a stretch to compare beginners and powerlifters, it isn't a stretch to say that many people have postural imbalances).
As far as hitting a new PR every time on linear progression, this is false. On linear progression you have a set weight for set reps and set sets, your goal for the day is to complete those successfully (it may be a PR weight, but also may not be, depends where you're at in the program). With ME days, you use set reps and most the time set sets, but you are trying to push the limit with the weight, which is the difference between 5-5-5-5-5 and 5x5 (I'm sure you're aware of that though).