The desired effect doesn't seem as strong when put like that. You can lock away $100,000 in order to access an extra $150,000 in borrowings, so really you are only able to access an extra $50,000, but your equity is locked up for 5 years.
BR
Not knowing the detailed ins and outs of cash bonds, if you are equity rich but serviceability poor they seem like a great idea. Even the 'loosest' lenders have a serviceability threshold, so these provide a mechanism to get you over the line.
BR