These lists are useful, though I think the hands you displayed are not the simplest examples. (This is intended for beginners).
Also, I would encourage beginners (as well as any other players) not to go into "signal-mania". Not every card has to be a signal. If I follow 3-6-7 instead of 3-7-6 I am not necessarily signalling anything. I may vary the order so as not to help declarer, particularly with a higher sequence like JTx.
Here I will give a simple example of why lavinthal-style discards are a good thing.
You're defending 3NT after the auction 1NT pass 3NT, and you lead the SJ.
[space] [space] [space] [space] [space] [space] [sp] Axx
[space] [space] [space] [space] [space] [space] [he] Qxx
[space] [space] [space] [space] [space] [space] [di] QJxxx
[space] [space] [space] [space] [space] [space] [cl] Jx
[sp] J9xx
[he] xxx
[di] Axx
[cl] xxx
You try a spade lead, which goes to your partner's queen and declarer's king, and declarer starts playing diamonds (king from hand first). You hold up, not because you can block off dummy, but because you want to get a signal from partner.
Second round your partner shows out - so his first diamond can't be a signal!.
Partner's discard should here tell you what to lead. You may need to cash out fast. Maybe he has AKQx(x) in clubs or AKQx(x) in hearts. Or perhaps he has stoppers in both hearts and clubs and wants spades continued, so you can set up tricks.
(Some examples)
Partner's (whole) hand is:
♠Qxxx
♥Axx
♦x
♣Axxxx
You must continue spades and your side will get 2 spades and 3 other aces. But if partner has thrown a spade, declarer will hold up the next round and your side will get just 1 spade trick and 3 aces.
Partner's (whole) hand is:
♠Qxxx
♥AKJx
♦x
♣xxxx
You must lead a heart and grab those tricks now.
Partner's (whole) hand is:
♠Qxxx
♥xxx
♦x
♣AKQxx
A club lead for 2 off