In general, dashboard voltmeters are only useful in relative terms as they tend to be damped and calibration varies unit to unit.
Check with a good quality voltmeter across the terminals of the battery.
12 volt batteries are rated as '12 volts' but their nominal voltage is higher - 13.2 is not unusual. The nominal resting voltage of a battery is affected by temperature, battery age, battery construction and level of charge, so again readings are relative and there is no reason to get your knickers in a knot if yours reads 13.2 and your buddies reads 13.4. (These are, of course, readings with no load on the battery and the engine off.)
In general, you charge a battery at a voltage 15% higher than the voltage the battery is nametagged at. That's where 14.4 comes from, and that is about where your voltage will be with the engine running.
The Jeep's ECU does not know anything about what voltage the alternator is putting out. It also knows nothing about whether you have an alternator rated at 90 amps or something else.
The voltage regulator INSIDE the alternator determines the voltage output. It varies the field current to maintain 14.2 (or thereabouts, depending on the design of a particular regulator). The current rating is the maximum that the alternator can put out. If you have a 150 amp alternator and the car requires 5 1/2 amps to run because you only have the motor running and everything else is off, your fancy alternator is putting out 5 1/2 amps. Switch on all of your DAylighters, and things change.
Voltage and current are two different things. Voltage appears across two terminals. Current (amps) flows through something. Together they make power (watts). Elegantly, in a DC circuit, watts = volts times amps.
Also, from Ohm's Law, voltage = amps times ohms (resistance). So now everyone knows why you install a relay when you add driving lights. The lights take a lot of amps, and a long and/or small wire has a higher resistance. Running long lengths of thick wire costs money and adds weight, so isn't it better to run thin light cheap wires to CONTROL the device, and a shorter fat more expensive wire to OPERATE it?
But I digress. Perhaps you should check the voltage accurately before drawing conclusions about what might or might not be happening, because those dashboard voltmeters are not necessarily conclusive.