Hello,
You should be aware that there are MANY dimensions that are NOT standardized by ANSI B16.9 for Welding Fittings. B16.9 standizes ent-to-end dimensions (and end-to-centerline dimensions)and the "squareness" of fittings but that is all.
The standard says that the fitting "must be able to be shown" to be able to sustain the internal pressure (at least) as much as the matching straight pipe. So, the manufacturers usually make them thicker (yes for elbows too - put that in your pipe stress model). The standard does not specify the thickness except to say that it must MATCH the matching pipe at the weld line.
If you look at B16.9 Tee's from 10 manufacturers you will see an amazing amount of dimensional variation. The crotch radii vaty greatly for example. Also some are "barrel shaped" and some are more "cylinrical". But they are all B16.9 Tee's.
Best regards, John