The actual width on the bike will vary with the width of the rim. A narrower rim will cause the tire width to get a bit narrower too.

I think it's the "inner well width" that really makes the difference. It seems like the outer width of the rim is more often published. Maybe there is a quite standard difference between these?

Anyway, if folks are reporting actual tire widths, it would be helpful to have some rim info along with it.