As someone who works at a very large company that is also affected by DMA, this is not how any company whose legal teams we've spoken with are interpreting this requirement. Data portability is being solved with export standards, so that users can (more) easily migrate to other services. Streaming someone's data over to another platform where they may or may not have an account, or ever intend to go, wouldn't fulfill that requirement, because if the user wishes to move to a non-federated instance, that would not be possible. Portability also cannot be 'favored' under DMA.
That is a separate issue from interoperability, which only works if Threads is allowing federated instances to fully interact with their users' posts, with no loss of functionality, which was at least originally not the plan.