Decoction essence is a myth.
Id bet pretty much every German Dunkel ( or beer short of hefe) you have ever had is step mashed. As Zee Germans have found since about 1970, that is does more hurt than good.
I think you mean Southern Bavarians and large industrial brewers, not all Germans. Definitely not the Franconians (not to mention the Czechs). https://beerandbrewing.com/slow-beer-frankish-style/ Homebrewing for many is a lot closer to old school, small family brewery brewing (open fermenting, for example) rather than large modern industrial brewing.
Right, most everyone has only had the macro Germans.
The frankonians/czech are certainly old word, and homebrew practices mirror that of those.
However they know about HSA, and will tell you about it, and their house flavor. Not to mention the beer travels horribly.
I would wholeheartedly disagree on helles being the primary style to brew low oxygen, though it is a prime example. But all other beer styles brewed by the same brewers that make these helles, are brewed in the same fashion.
We had a decoction only brewer born and raised in Munich, when we started out with the group that brought this forward. Lets just say he has stopped decocting. Not to say YOU can't do it, but on our scale, especially with non specialized homebrew equipment, it won't be as good of a beer in the terms of the low oxygen beers. Not to say it won't be a good beer, but in these terms (low oxygen brewing) you will have a better product, since oxygen mitigation is paramount.
By all means though, brew how you want too.