I think you are referring to warrants being redeemed, not exercisability
S1 excerpt
No public warrants will be exercisable for cash unless the Company has an effective and current prospectus covering the shares of Common Stock issuable upon exercise of the warrants and a current prospectus relating to such shares of Common Stock. Notwithstanding the foregoing, if a prospectus covering the issuance of the shares of Common Stock issuable upon exercise of the public warrants is not effective within 90 days from the Closing, warrant holders may, until such time as there is an effective prospectus and during any period when the Company shall have failed to maintain an effective prospectus, exercise warrants on a cashless basis pursuant to an available exemption from registration under the Securities Act. If an exemption from registration is not available, holders will not be able to exercise their warrants on a cashless basis.