Other than being fun; I can't quite see the benefit of making my shell more verbose. I'm sure I am not the only one who can get by with the regular commands through mnemonics.
And to further my point; if this was such a good idea, then why has nobody aliased 'ls' to list, 'cp' to copy, (etc.)? Or, while we're at it, 'list files', or 'list files in current directory'. Maybe someone has and I just didn't meet them yet.
I do see the point of a programming language to be a bit more verbose, since it makes sharing between humans easier, as understanding old codebases – but even there, people are split (Java is too verbose! Ruby is natural! Lisp is too much abbreviated! etc.). But using a shell, issuing commands, is fundamentally different to programming, in my opinion. Consider the analogy of a crane (just to avoid cars for once), what would you prefer: Waving your finger around in thin air, or using levers? And before you answer that: while the former seems way more cool, it doesn't work well. Getting rid of mechanical controls has been tried experimentally by the Air force (I read that back in the 90's; sorry no link to a source now): They were able to interpret commands from the pilots brainwaves, but manual control was consistently faster. We humans just evolved this way: Thinking of moving a plane into particular direction is slower than moving your hand accordingly to yank a stick – it seems to have a higher more mental load for us. Do you picture your arm moving your mouse? I bet you "just do".
But I digress; though the fundamentals in play are the same. My fingers are fast; why should I slow down the whole thing by making them type more?
Of course, a shell using of single-letter commands would be equally useless to an overly verbose shell. The sweet spot, in the end, might be a personal preference and dependent of daily usage and experience. In my case, that's a bit more than the POSIX command set, and – to exaggerate a bit – not writing essays on the command line.