Yeah, I'm not sure what the confusion between volts and amps here is... but the rating of amps is the maximum that a power supply can provide. Electronic devices have an average and maximum that they need to draw, and the power supply has an average and maximum it can provide.
For example, I've got 12 guitar pedals that all run 9v and I agree with you the power supply must be 9v. They are daisy chained together so that they all only need one power supply. My power supply provides up to 2700ma of power, and the pedals consume about 1700ma of power on average, which ensures that all of them can operate and function properly within the specs of the power supply. So I have plenty of headroom if I wanted to add another pedal, but there is no issue that the devices in the chain consume less amps than the power supply can provide.
I agree with you that devices that consume more amps than the power supply can provide can absolutely shorten the life of the device or the power supply, and you absolutely should not do this, and you absolutely need to match the voltage specifications. I'm not so sure what you're concern with a power supply providing the ability to draw more than the device needs is though. Maybe I am misunderstanding something, but there might be a misalignment of terms.
"Many people are confused by amperage ratings and what they mean when it comes to power supplies and replacements.
The amperage rating is the maximum amount of power it can supply.
One way to look at it is as if amperage were “taken” (often referred to as “drawn”, as in pulling) by the device being powered. That device will only draw as much amperage as it needs to perform whatever it’s doing. Your computer will use more power, in the form of higher amperage draw, when it’s working hard than when it’s not. (Voltage remains the same regardless.)
Thus, as long as you replace your power supply with one capable of providing as much or more amps than the previous supply, you’ll be fine.
If for some reason your replacement power supply has a lower-than-required maximum amperage rating, you may end up with a burnt out or overheating power supply, and the device itself may not function."
From
https://askleo.com/can_i_use_a_charger_that_provides_the_same_voltage_but_a_different_amperage/