Forfeitures differ from most cancellations because they are designed to be unilateral, even though they use the same form 484 as bilateral cancellations to report it to ASIC.
The forfeiture provisions are designed to provide a means for companies to cancel shareholdings for which they have not received payment. These are usually subject to Call on Shares requirements in the company constitution (i.e. demand payment, wait a set period, cancel if no response).
As shares are property, they are very difficult to get rid of unilaterally. When a member is issued unpaid or partially paid shares and then disappears, the company is left with little recourse to get them off the books outside of a forfeiture.
As the nature of a forfeiture is such that the company is forced to cancel the shares unilaterally, this is why there is no agreement or consent from the shareholder. If there were consent, it wouldn’t be a forfeiture so much as it would be a redemption or some other similar transaction.
If someone lodged a share cancellation with ASIC using the forfeiture tickbox and they lied about it then the shareholder can take legal action. This scenario exists outside of the proper use for a forfeiture.
Edit: missed half a sentence, added it in.