You don't understand, your data is not deleted that frequently. Your transaction is still linked to all transactions perhaps not back to the beginning but plenty of data.

It's just that the transaction after that will no longer be open to dispute.

To give you an analogy, it's like if you build a chair with your own hands and many tools, you throw away all the tools and the byproduct after the chair is finished.

So after the transaction data is deleted only the hash will remain which will contain proof that your data is linked to the early data, but the early data is no longer needed.