Tree Supports never start from model?

[CasaDelGato 1]

I have a large model that has several odd brackets on top that do need supports.
These brackets do NOT extend out beyond the edges of the large block they are on top of.
When I turn on Tree Supports - the supports start at the baseplate, extend all the way up beside the model, then finally curve in to support the brackets.
Why don't they start at the top of the main block of the model instead?

[twlum 3]

Tree supports are designed to support the overhangs without touching the actual model. 

Take a look at this video for a better explanation:

 

[CasaDelGato 1]

Thanks, for some reason that just hadn't registered in my head.  My previous uses of Tree Supports were on models with lots of overhangs.