"have I got this right? In order to be a 'computer whizz' I have to forget about using the mouse and memorise somewhere between "11 pages" and "more than [I] can possibly imagine" shortcuts, do I?"

Nope!

These often 'historical accidents' shortcuts have been passed on 'to be compatible' often from systems (Such as Mainframes) long predating Personal Computers. They CAN be useful, as they (such as the copy, cut and paste ones) tend to be consistent across ALL computers, all Operating systems and MOST programs. Some of these are 'Microsoft special' things that have spread 'for compatibility'. They CAN save some time over 'mouse actions' - but only if you getup to the speed that needs them.