It's a TSX Exchange rule.  Denselight is definitely more than 50% of Poet's current assets.

https://www.tsx.com/resource/en/444

Shareholder Approval

5.14 The Exchange generally requires shareholder approval for:

(a) any transaction which results in the creation of a new Control Person;

(b) any transaction where the number of securities issued or issuable to Non-Arm’s Length Parties as a group as payment of the purchase price for an acquisition, exceeds 10% of the number of outstanding securities of the Issuer on a nondiluted basis, prior to the closing date of the transaction; and

(c) a Reviewable Disposition which is a sale of more than 50% of the Issuer’s assets, business or undertaking.