We encountered the same data sharing screen when filing the already completed tax return. It seems that we were able to decline data sharing. After clicking "Review and Sign" within that screen, we were able to click "No thanks" without entering a name.
I agree that Turbotax is becoming too aggressive about pushing its products to already paying customers. Data sharing with third parties should not even be permitted in conjunction with anything as sensitive as a tax return.
If Intuit continues to want to coax tax filers into this, the data sharing screen should appear early in the tax return process, and the default should be that nothing is shared. Only opting in should require an action beyond clicking "Skip".
