But really for most meetings, the individual doesn't need to be fully mentally involved
Dyslexia may explain why you don't need to be fully involved. It's my understanding that a lot of things work differently in the dyslexic mind vs. the non-dyslexic mind. Some are good, some are bad. Ask Richard Branson, Scott Adams or Steven Spielberg.
However, most of the population isn't dyslexic, and for them to contribute to or benefit from the meeting, they do indeed need to be fully mentally involved. What works for you doesn't necessarily work for your coworkers, or neighbors, or...
If you really feel that you don't need to be attentive, I'd suggest that you show some respect for your coworkers and simply dial in to the meeting. You'd be showing respect to them by not behaving in a way that annoys the crap out of them, while you're right in front of them.