RE:Question "If less than 50% of the shares are tendered, does Delek have the option to acquire these shares, thereby increasing their shareholding beyond 20%?"
"Take up and payment for the shares is subject to a minimum tender condition that requires more than 50% of the common shares being deposited pursuant to the Offer"
https://www.ithacaenergy.com/media/news/recommended-takeover-delek
"50% Minimum Tender Requirement: Take-over bids are subject to a mandatory, non-waivable minimum tender requirement of more than 50% of the outstanding securities of the class that are subject to the bid, excluding those beneficially owned, or over which control or direction is exercised, by the bidder and its joint actors (the Minimum Tender Requirement)."
https://www.osler.com/osler/media/Osler/reports/mergers-acquisitions/Canadian-Public-Company-M-A-Guide-2016.pdf
Furthermore, people tend to think that the management has already render all their shares, but:
"In the event that Delek does not take up its right to match a Superior Proposal (as defined in the Appendix below) and Ithaca terminates the Agreement in accordance with its terms, the lock-up agreements will automatically terminate."
I have a feeling that the guys have just been "politically correct" knowing that this bid wouldn't go through...just my opinion.