Well I was about to offer another explanation of what BFL was alluding to, but...
you seem to have come to the right conclusions regarding the nuances of flooded batteries. In the bulk stage, voltage is less important. 13.6V is enough to supply 80A from a simple charger. The Vectors are a good example. It's during the absorption stage that voltage becomes more the main factor.
If you really have gotten to the bottom of the PD's "issues," that sure would be cool!
I have always wondered if PD didn't design their units to operate on the conservative side when it comes to safety. That's better on company insurance premiums vs. heating up some non-techie's bank to catastrophic failure. Bigfootford is a big proponent of maintaining a modest temperature while charging. Certainly with AGMs you've got the possibility of thermal runaway. No bueno. And with RVers duped into thinking AGMs are the cat's meow, all it would take is one guy to charge his AGMs with an IOTA on a sunny August in Yuma...
As a techie, bigfoot likes the control of being able to throttle his PD down on a hot day where a hyper fast charge is not a requirement. And there is certainly some validity to this line of thinking.
That said... Sal says he never has any problems with his IOTA driven setup.
Again... would like to know if PD designed their Charge Wizard this way on purpose.