However, precedents can also be changed by the court system. So using the FTC as a lever to change precedent is in fact potential route to change the law. It may even be the only option with congress's dysfunction.
This isn't the FTC denying these arbitrarily though so isn't just "executive action", this is using the enforcement making power that congress duly granted to agency to bring law suits. If the courts agreed that precedent needs to change that's checks and balances working.
Please tell me what major question this is violating? Anti-trust law is explicitly given in its ability to bring suit to these companies. The consumer harm standard isn't even a part of the law arguably the consumer harm standard should be overturned by the major questions doctrine since the court wrote the rule into the law wholesale without congresses directive decades after the law was written.
Both are, the FTC was created with shared jurisdiction on matters of anti-trust. However, the supreme court recently limited that to injunctive powers https://en.wikipedia.org/wiki/AMG_Capital_Management,_LLC_v.... relief would be through a DOJ suit or via state AGs