The applicable ASME construction codes, i.e., B31.1, B31.3, etc. does address the extent of the weld required.
Weldolet is a trade name. The generic term is integrally reinforced branch fitting. A sketch is provided indicating the weld is a complete joint penetration groove weld with a reinforcing fillet weld.
You should also read the literature available from the manufacturer. They usually have illustrations available on their websites depicting the extent of the weld required for them to function properly.
Note one thing, the extent of welding is not a function of the design pressure. That is, whether the system operates at low pressure of high pressure, the same amount of weld is required.
Best regards - Al