However, in the case of the Remington 870, which is the gun the OP is asking about, I have to disagree. The safety becomes easier to use with a SF IV or SF IV-S stock especially if used with a Vang Comp BHS. I find every aspect of shooting a "fighting shotgun" easier with the IV-S than the conventional stock.
That may be your personal experience. I tend to reflect on what I have seen over a couple of decades training people to use the shotgun in fighting situations, and that experience has shown the regular design stock works out much better for most situations than does the pistol grip design, be it Mossberg, Remington, Winchester, Beretta, or others. Shortening the LOP does make quite a difference to the good, but the pistol grip does the opposite. YMMV.