It will make a difference on follow up shots you are mounted to barrel nut which is a transition piece, chamber is in the barrel not the receiver so heat, and extraction can cause a shift. . Also check barrel nut after 100 rounds this is not a 223 have had correctly torqued nuts loosen on an Alexander Arms upper ,what made me check point of impact was changing with each shotHi,
I guess it is just another thing to do to maybe keep one part from effecting another.
In my World heat expansion is probably not a factor.
However, the sling tension was a point and maybe lights installed?
I'm still building, so did it while easy.
Seems some rail makers mention it and some don't?