No, thats normal
Just after startup battery voltage should be 14.4-14.8volts, this is a "fast recharge" in case engine stalls and you have to use battery again
After 5 minutes or so it will drop under 14 volts, 13.4-13.8volts and stay there until next start up
Sensors all use a regulated power supply, like 5 volts, so it doesn't vary with system voltage(engine running voltage)
What you are testing on MAF sensors is its Heater, not the sensor, heater is not voltage sensitive
Battery is only used to start an engine, after that the alternator supplies ALL the voltage, 13.5v average, battery is only 12.3v to 12.8v so alternator voltage goes TO the battery to keep it charged up for the next start up
All the sensors use a reference circuit, so what is used is a comparison voltage, a voltage difference, not that actual voltage
If computer sends 5.0v and gets back 3.0v the 2.0v difference is used, not the 3.0v
Now if computer sends out 4.8v and gets back 2.8v then sensor reading is exactly the same, 2.0v difference, this allows for "graceful aging" of equipment, lol