I find that I can create a tagged PDF. I can create a dynamic PDF. But I haven't been able to create a tagged dynamic PDF.
I created a simple form in Designer 8.1, set it to be dynamic and to generate tags in Acrobat. I opened it in Acrobat 8. Under Advanced > Accessibility > Full Check, I selected Adobe PDF under Checking Option. The test failed, saying the document was not tagged and contained no fonts. But if I resave the form as a static interactive form, it passes the full accessibility check with no problems.