At its core, It's an ultra-low-power microcontroller, and the low-power requirements to hit the battery life specification while maintaining audio quality may or may not allow the kind of software abstractions that make these codecs "just software". Once you've licensed the codec, you then have to implement it on the micro's architecture, in a way that's actually performant. Which in turn may or may not require actual Assembly work.
The constraint throws off all the calorie math in regard to exercise. You find that no amount of exercise helps at producing lasting weight loss even if the meter/app says you burned 700 or whatever, which is .2 lbs. If you do this for 10 days you should lose 2 pounds of fat , keeping diet constant, but you don't. Either you lose less or just water.