With the rear of the bolt tightened up and both front lugs making contact, the bolt MUST align. In addition, the primary purpose is to prevent deflection of the bolt due to pressure applied upward by the sear. The boring of a receiver and sleeving of the bolt, while beneficial from an alignment standpoint, is not really suitable for a field rifle where feeding and function under adverse conditions are important considerations.
As far as the advisability of straightening up a commercial action, as compared to the purchase of a custom action, is concerned, it's just a matter of approach. Methodology is developed for truing and improving standard actions because there has been a demand for it. From a gunsmithing perspective, a skilled workman, like Dennis Sorensen, may take some pride in doing what he does. Anyone with rudimentary machine shop skills can fit a barrel to a custom action with reasonably good results (this assumes the custom action is perfect; this is not always the case). When Dennis trues up a Remington action and fits and chambers a barrel to it, it is, to some extent, an expression of his ability. The more the gunsmith does to achieve an end, the more of himself is put into the final product. So, for the gunsmith, he can simply attempt to buy perfection, by supplying a custom action, or he can attempt to produce perfection.
For the customer, he buys quality either way. In one case it is a product from the hands of a skilled workman. in the other it is the product of the finest computerised machinery money can buy. It's all a matter of perspective.
I first started doing the dovetailed inserts because I was asked to remedy a perceived shortcoming without compromising function in the field. In essence, I was simply devising a remedial method to duplicate what some custom action builders were doing with their initial design. This was the easiest way I could come up with and, since I am inherently lazy, easy is good.