Is it just me, or is this an unusual clause in a contract of sale for a house and land:

Extension of the Settlement Date

.1 In the event that the vendor shall be strained or prevented from completing this contract in accordance with it term by injunction, warrant, caveat or otherwise the vendor may at its option:

1.1 rescind this contract by notice in writing to the purchaser, whereby the contract will be deemed to an end and all monies [...] refunded; or

1.2 [...] extend the settlement data for a period up to 60 days [...]

Is this typical? reasonable? gazumping?