Making the most out of stock
From a culinary viewpoint, there is little to no reason to use bones more than once in making stock.  Even the author of the article you reference indicates the first go is the one that tastes best.  

To maximize the quality of your stock:


Use good clean or filtered water; add hot water as the stock reduces over time to keep the level above that of the bones
Use good bones, chopped with a cleaver to reasonable sizes (a few inches)
Optionally roast the bones prior to stock making for a deeper, browner flavor
Skim the scum in the first part of the stock making process (obviously not an option in a pressure cooker)
For a more clear stock, don't allow it it boil, but rather than let it go at a slow simmer (again, not in your control with a pressure cooker)
Simmer it long enough for reasonably full extraction, which will leave the bones either bendy (more in the case of poultry or long bones) or somewhat fragile
Include good quality vegetables for flavor
Don't salt the stock, as during reduction it can concentrate and become overwhelming


In other words, apply basic cooking common sense and you will have a good outcome.