The two different arguments people are having
Either the will is invalid, or the will is valid but unfair.
A family provision application does not say the will is wrong. It accepts the will and asks the court to order more provision because adequate provision was not made for the applicant's proper maintenance and support. Eligible applicants in Queensland are a spouse, which includes a de facto partner, a child, which includes adult, adopted and in some cases stepchildren, and a dependant.
The court weighs the size of the estate, the applicant's financial position and needs, their relationship with the deceased and any competing claims. A validity challenge is a different argument entirely: that the will-maker lacked testamentary capacity, did not know and approve its contents, was unduly influenced, or that the will was not properly executed or was forged. There are also disputes that are neither, about what an ambiguous clause means, or about an executor who will not account, will not distribute, or has a conflict of interest.