I like to think of IM as surfing probability. Every moment is the collapse of a wave of probability and how things unfold is highly dependent on how things currently are. Although, anything is possible. I recall watching an interview with a physicist and it shocked me when he said that there was a probability that he could be instantly transported to Mars. That probability, of course, was extremely small. That statement sparked in me that anything really is possible.
Anyway, IM is about using intention to play the numbers, to increase the odds of a certain event occurring. So, theoretically, yes, a one-armed man could will his other arm to grow back but it would take such a monumental amount of focus and certainty (likely a superhuman amount) that it wouldn't be worth the result... maybe 1000 years from now, such results will be within the realm of practicality.
But to answer the OP's leading questions, yes, I don't work with the LoA because it can only do what will likely happen anyway
