It depends on the code of construction. For example, Section I for Power Boilers exempts PWHT for application of non-load bearing studs - see below for General note 5 from table PW-39-4.
(5) for welds attaching nonload‐carrying studs or insulation attachment pins not exceeding 1/2 in. (13 mm) in diameter when using an automatic arc stud welding or automatic resistance stud welding process