FYI - There is a difference in the profile of your 300WM Selous barrel and 375H&H Selous barrel.
If you look closely at the caliber chart, there is a note (7) next to the tick mark for the 300WM and 300BLASER Selous barrels. They are 19mm but retain the barrel band sling swivel and brass bead front sight. All the other Selous barrels are 22mm. I also measured this because my wife has a 300WM Selous barrel.
For a while they made “safari” barrels that were also 22mm (but not in 300WM). The difference with these is that they deleted the barrel band sling swivel and the brass bead front sight found on the Selous. I believe
@TOBY458 has a safari in 458WM. Last I knew the safari barrels had been discontinued.
Here is a picture that
@TOBY458 posted. The bottom left rifle has a Selous barrel, and I believe the one next to it (bottom middle) is a safari barrel. Would need him to confirm this.
View attachment 655556 The rifle in the middle is a 416 REM Mag Safari barrel. The 458 on the left is a 458 Win Mag. I believe you are correct about them no longer making the Safari barrels. The Selous barrels are all they make now, if I’m not mistaken.