Hi @Jeremiah_Rose ,
You are abosolutely right!
The ACS712 does not support 3.3V, at least in their datasheets.
However, in my tests I was able to run them consistently at 3.3V without any issues. 
Also if you use them at 5V rather than on 3.3V. The gain is 0.185 V/Amp and the range of 5Amps would give you the voltage range:
[ 2.5 - 5\times0.185,\quad 2.5 + 5\times0.185 ] = [ 1.575,\quad 3.425]
So it would be just shy outside the range of the 3.3V adc input. The max current you could measure with a 3.3V adc would be
(3.3-2.5)/0.185 = 4.32Amps
Hope it helps!