I can’t speak to which superguns do what, but I tell you that the problems I believe you’ve read about involved the Windy [City?] Gaming supergun, which had two major problems: first, it had (still has?) a switch on its rear to toggle whether line-level or amplified audio was sent to the SCART output, which is incredibly stupid, because you should never feed amplified audio to a SCART device–it’s way out of spec.
The second problem is that that switch was unlabeled, so those who bought this supergun had no idea whether they were sending line-level or amplified audio to their SCART equipment. Those that did end up sending amplified audio to their SCART equipment ended up burning them out.
The third problem was that the creator of the supergun/owner of Windy [City?] Gaming, as I understand it, vehemently denied there was any problem and refused to correct the unlabeled switch problem in future production runs.
It doesn’t look like Vogatek really publishes any product information on what I think is their current website, vogatek.com–even their About Us page is entirely devoid of content; so it’s not clear to me how their superguns handle audio. Hopefully someone with experience with these devices can chime in.