Ok well apart from the fact that there is no such thing as a standard dB and when someone states dB it could literally mean anything, it doesn’t even have to refer to sound with no other information it could be referring to the number of pigs in a field. This means there is no way of comparing a simple statement of this will reduce by 38dB with anything else unless there is more details (weighting, metric etcs).
One glazing specification will give you 3 different levels Rw, Rw C and Rw Ctr. They are all dB reductions and can legitimately be given for the sound reduction of the window, and that is why we get paid to specify façade mitigation rather than the developers or architects simply reading a dB number on a web page.
The data is all from the same testing methodology, but the BS doesn’t cover all possible glazing specifications, frame specs etc make no noticeable difference to the sound reduction of the glazing system.