"Truing" or "Blueprinting" a receiver has several different definitions depending on who you ask but I'll give you my take on it.
After owning and working on numerous Remington 700's I can say this with 100% certainty, I have never seen a Remington 700 receiver that was completely square, concentric or perpendicular with any surface within. The bolt lugs seem to be a different story though and are usually perpendicular with the bolt body.
I manufactured a receiver truing collar for the purpose of truing the receivers while being held in a rigid setup. The receivers are indicated in this fixture by the means of a Brown & Sharp .0001" Indicator reading on a .500" hardened, ground mandrel that’s held in the bolt raceway by tight fitting bushings. I have several different bushing sizes that allow me to find the perfect fit between bushing and bolt raceway. Often, the difference between the front and rear receiver ring ID is as much as .002" making it impossible to use one mandrel for all receivers.
Here is my method;
http://www.louisianaprecisionrifles.com/blueprinting.aspx
Once dialed in to .0002" or less TIR measurements can be taken at the receiver face and lug abutments to determine just how much TIR there is in the receiver face and how much perpendicular difference there is between each lug abutment face. I've seen lug abutment differences as much as .002" from one another and TIR of .004" on the receiver faces.
I stopped trying to measure receiver threads because to be quite frank, I didn’t have a very good method of doing so. I decide to just make a clean up pass on them with a full profile threading insert and the single point method. I wasn’t shocked to find out that the vast majority of receiver threads failed to be concentric but some were also tapered or offset. Taps and or hand tools will not address this issue and only debur and or clean out the thread root.
Factory recoil lugs are another issue and should be addressed be either surface grinding them or replacing with an after market version. I prefer a hardened, ground custom recoil lug. To answer your question, yes receivers should be trued in a manner as I described above along with the bolt lugs and bolt face. When receiver truing is performed correctly, barrels will align straighter in the receiver and tighter barrel joint threads can be cut, shoulders will lock up tighter, chambered rounds will have less negative influence when the bolt is closed and the bullets will start straighter in the throat reducing bullet deformation when fired resulting in tighter groups and more X’s or a higher dog count a the end of the day.
