The DSA contains provisions for combatting disinformation and as a very large online platform google is required to implement suitable practices. The DSA is a regulation, that is, immediately applicable law in all of the EU. As is usual for laws it’s written pretty generically and abstract, though, so the commission is also publishing more detailed documents that companies can use as check-lists.
In essence, the difference between the tax code and the finance ministry publishing a paper on accounting best practices. You’re free to ignore the latter but that will likely make your life harder that in needs to be.
The only reason the regulation happened is because Apple ignored the “industry, agree on a standard or we’ll set one for you” memo: By the time the EU passed the act all other manufacturers had already shaped up.
That is: For other companies, the looming threat sufficed. Apple needed to be forced.