Owner builder LVR of 60%, but what if the owner IS a builder?

It is my understanding that owner builders are subjected to tighter LVR restrictions of about 60%. I assume this is because there is a higher risk that an inexperienced owner builder could have a large budget blow out and not complete the job. Leaving the bank with an unfinished asset to sell off.

If the owner has a fixed price contract with a builder the risk of a budget overun or incompletion is much less, so a higher LVR is allowed.

My question is, why is a registered builder subjected to the same LVR as an owner builder when financing for their own new home?

Surely the fact that a builder spends everyday estimating and budgeting for building work during the course of their business the risk of a budget blow out on his own house would be reduced. Also the bank only releases the funds upon inspection of each stage so its not possible to run off to the TAB and put all the loan on a horse, or use it for other purposes.

Another interesting part of the banks view of this situation is that the builder/owner builder must get another builder to sign off on the budget for his own house.

I would have thought that being a builder would be an advantage when seeking finance for their own home.