The difference is that if you see boost mode (14.4v) the 9 amps into the converter will hold for 60 to 90+ minutes instead of 30 before it starts tapering.
You can check around all you want to check the system and with great effort you may or may not ever see boost mode.
The real measurement is the voltage right off the WFCO converter during the first 2 minutes of charging. This voltage right at the converter needs to be somewhat below 13.2 volts to trigger boost mode and is actually fairly difficult to achive. Been through this years ago. Far better to just get a new converter that works as expected.