The copyright law in many countries contains a specific interoperability exception that explicitly allows such cases to enable "information exchange".
"Courts have recognised that reverse-engineering is important for public benefit and to encourage inventors and businesses thereby maintaining healthy competition in the market".[0]
Yet most technology giants are based in the States thus do what they want - within the permissive laws of their country. It's ironic how the folks here on one side get upset every time Google/Meta does something evil, yet at the same time get upset when the EU does something against Google/Meta.
It is unclear whether a third-party client that accesses content you are otherwise licensed to access is actually infringing, and it's likely to differ in many countries as well.