Update: Note that it is carefully worded: "Our directors, executive officers and holders of a substantial portion of our capital stock and securities convertible into our capital stock".
What probably happened is that the company required holders of only a "substantial portion" of stock to sign updated agreements with the underwriters. Neither I nor any of my Lyft stockholding friends ever entered into such an agreement (and Lyft isn't claiming that we, as minor shareholders, did). So as far as I can tell, nothing blocks us from hedging with Morgan Stanley or otherwise.
(Original post was thinking the S1 is wrong; it is not)