If PFE sold more than 20% the 1st transaction would demand capital gains.
I don't see that at all. The Newco will issue shares for the 20%. Technically I think this whole transaction is termed an "equity carve-out."
Thinking more about it, retaining 80% is crucial for the dividends-received deduction as well as the ability to subsequently spin.
Historically, I believe these 2-step versions (equity carve-out followed by a spin) have performed better than a pure spin. The reason I believe is pricing - in a pure spin none of the shareholders know what their shares are worth and many just dump them. In an initial IPO, you get the IPO process to establish a fair price.
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