The DMA might be referred to by some as "asymmetric regulation" because it's a framework that encompasses more than just antitrust. That's a charitable explanation for saying that. But I think most would colloquially understand this as antitrust law because the motivation and similarities in approach composes a great deal of the framework. The vast majority of writing discusses the DMA as antitrust law and I find very little to suggest that your definition distinguishing the DMA apart from being antitrust law is widely accepted. I think the distinction would be better stated as "antitrust regulation" vs "antitrust enforcement".
One article that did support your definition:
https://www.bruegel.org/blog-post/how-european-union-can-best-apply-digital-markets-act
However, that was the only article I could find discussing it in this way.
The focus on whether Apple is a monopoly here is a bit of a side tangent I think. I asked a question about monopoly power in a hypothetical scenario because that was intended to address some claims regarding contract law, but i don't recall claiming Apple was a monopoly or that the DMA turned them into one. Apple is floating in a grey area that's probably around market dominance to oligopoly or duopoly ... certainly enough to get the attention of regulators on multiple fronts.