I've seen nozzles that consisted of weldneck flanges welded directly to the vessel.
The fittings and their design would be dependent on the design code, i.e., whether reinforcement was needed, etc.
I suspect the fitting in the photograph would have different trade names depending on the manufacturer. They look like half socket couplings to me. I couldn't tell if they were integrally reinforced branch fittings from the photograph. I doubt they are IRBFs because I could not see a beveled edge where the tack welds were located and I did not see any radius where the fittings butted up against the vessel wall.
As mentioned, I could not tell if these were branch fitting welded to a run pipe or if they were welded to a vessel.
Merry Christmas everyone.
Best regards - Al