Possibly so for now. But do you think the providers are interested in making interoperability easy?

Even in the future if they are required by law to provide it, I wouldn't bet against the craftiness of the providers to invent some sort of network effect dark pattern to make it painful, if not outright impossible.

Just as an example, with Muse I can already see that the way they are thinking of making money is via taking a transaction cut, so it's not that hard to imagine that Meta can negotiate deals for txns that happens through Muse which won't be available elsewhere.