SS3 Raditz and Nappa in Heroes

[Captain Cadaver]

In the DBH games, Raditz and Nappa bypass SSJ completely and instead go straight to 3. Even though this can seem like more of a marketing ploy due to a greater difference in design, it is worth noting that they achieve the forms in some anomalous rift in dimensions and that the mentor Nappa in DLC only achieves SSJ when in a city that seems to functions by the same physics as DB's Earth.

Taking this into account, as well as SS3 Vegeta's profile in Raging Blast stating he gained the form in Other World (likely in some alternate timeline after his sacrifice against Boo where he had time to train), does what is otherwise a collection of shallow fanservice actually help further confirm the hypothesis that SS3 is a form only attainable through training outside of the mortal realm?

 

[SSJ2]

Wouldn't that only apply to Goku because he was dead? Being in a different dimension or not, the user would still be subjected to SSJ3s immense strain if alive.

 

[Captain Cadaver]

Being dead helps handle the strain of the form, though clearly isn't the catalyst for attaining it, and it requiring something more than the mortal realm could supply would line up with Gotenks attaining it through Rosat training.

 

[Papasmurf]

I think Toyotaro seems to roll with the idea that SSJ3 is unattainable outside of an alternate dimension judging by the fact that Trunks' FPSSJ2 is almost equal to SSJ3, yet he never attained it himself. The Super anime will probably contradict it at some point with SSJ3 Caulifla or some shit, judging by their track record. Until AT or a supplementary Chozenshuu volume goes out of its way to confirm that SSJ3 needs to be attained in a different dimension though, it's just headcanon for the most part.