I'm not familiar with Contractual Wills, but if asset protection after you pass away is important, another option you might like to check out is testamentary trusts.
Overrated in my view for AP whilst you're still on this mortal coil. Also think mutual wills/will contracts are less than ideal for when you die. TTs provide flexibility and tax advantages.
contractual will is one in which A contracts to leave B property upon the death of A. If A changes its mind and doesn't B can sue A for breach of contract. Not sure how this could aid asset protection while A is still alive but B might be able to argue they have an equitable interest in the property. Depending on the circumstances I would say they generally would not until the death of A.