Funny he should mention about not using the CD input (Tip 5).
I'm not sure how relevant it is on modern amps, but certainly on many older amps the best-sounding input was often the tape input, particularly if it had a dedicated analogue switch for tape monitor. The reason for this is that it was common for the other inputs to pass through lots of extra 'pre-amp' circuitry, while the tape monitor input (and switch) was often patched in much later up the chain, often just ahead of the volume control. The difference is (or was) very noticeable.
With regards to the kind-of-linked Tip 15, how relevant it is today I'm not sure, because few people use recorders that take an analogue feed from the amp. Some amps have selectable tape-out controls which you can set to a source you aren't listening to. The alleviates the need to unplug the recorder. But if you haven't such a control and you have an analogue recorder connected to a modern-ish amp with a passive pre, then I agree unplugging the recorder does make a difference as it removes the unnecessary load on the playback device (eg the CDP).