It's not *not* normal, but those aren't the default channels. Defaults are PU1 = MIDI channel 1, PU2 = MIDI channel 2, WAV = MIDI channel 3, NOI = MIDI channel 4.
However, the teensyboy firmware loads values for the output channels (and a bunch of other stuff) from EEPROM, so channel 16 etc. must be stored in EEPROM for some reason.
One fix would be to open Arduinoboy1_2_3_teensy.ino and edit:
boolean alwaysUseDefaultSettings = false;
to read:
boolean alwaysUseDefaultSettings = true;
Then recompile and upload to the Teensy.
That's assuming the default channels are what you want.