My understanding why this is usually not discussed is the following: The fibonacci sequence is usually used as an illustrative example or motivating problem for

My understanding why this is usually not discussed is the following: The fibonacci sequence is usually used as an illustrative example or motivating problem for a given topic, not as a problem in itself. I believe a side note might most likely detract from the overall point for a technicality. For the same reason you only wrote "if you consider exponentiation to be a constant time operation" instead of including a side analysis of how everything changes once you can't do that anymore, possible problems with accuracy of floating point representations of phi and it's exponentiation and everything else one has to consider once we leave the comfortable home of architecture native integers. It is usually very valid to do so.