Multiple documents with Auto-Place not using DocumentId

I am creating an envelope using the API and adding multiple documents and using Auto-Place to add the “Sign Here” tabs. The anchor string is the same on both documents but I would like the tabs to only place on the document specified by the “DocumentId” on the tab. This does not seem to work.

Here is example code using the C# SDK:
Is it expected that the SignHere would be added to both documents? If so, how would I prevent that?

	var envelope = new EnvelopeDefinition();

	Document doc1 = new Document
	{
		DocumentBase64 = doc1DocxBytesBase64,
		Name = "docusign-test",
		FileExtension = "docx",
		DocumentId = "1",
	};

	Document doc2 = new Document
	{
		DocumentBase64 = doc2DocxBytesBase64,
		Name = "docusign-test2",
		FileExtension = "docx",
		DocumentId = "2",
	};

	envelope.Documents = new List<Document> { doc1, doc2 };

	var signer = new Signer();
	signer.Name = "Test Name";
	signer.Email = "test@test.com";
	signer.RecipientId = "1";


	SignHere signHere1 = new SignHere
	{
		AnchorString = "\\s1\\",
		DocumentId = "1"
	};

	Tabs signer1Tabs = new Tabs
	{
		SignHereTabs = new List<SignHere> { signHere1 },
	};

	signer.Tabs = signer1Tabs;

	var recipients = new Recipients();
	recipients.Signers = [signer];
	envelope.Recipients = recipients;


	envelope.Status = "sent";
	envelope.EmailSubject = "This is a test";


	envelopeApi.CreateEnvelope(AccountId, envelope);