Your understanding is partially correct in that the 10th word could appear anywhere in the cipher, not just located in the tail.
Why is it only partially correct? Because in a ciphertext of 6 columns x 12 rows, if two rows are taken out to mark the rule, the remaining 10 rows cannot possibly correspond to the 12 seed words.
So it's impossible to use 6 letters for each seed word, right?
That's a good point. For example, the word "brisk" comes with position "2". But, what do you mean with "can be placed out of order"? I understand it as "if we have a word and its position, then the order is irrelevant to us". For example, LwE~T1 could be the word "property" along with the position "10".
This actually comes down to personal habits, I've been using PassCards for quite a few years, and the cards themselves have been iterated through a few versions, and every time I upgrade I change all of my old passwords with the new card, so there are always a few characters in my password rules that are version descriptions, and I've found that it's a good habit to have, so that I can manage my business- and work-related accounts on one card, and my family- and personal-life related ones with another card, and my digital asset accounts with a completely different card.
I'm assuming that there are others out there who have the same habit as I do of using multiple cards/multiple sets of cards for separate purposes, so it wouldn't be a bad idea to add a card identifier to the rules when it comes to secretly writing seed phrases.
But, we only have one black card with two sides. Not entirely sure why you would want sets of such cards.
The answer to this question really varies, and I read a story here named "
How do you safely keep your recovery phrase written on paper?". I believe many people, especially newbies, are faced with this choice of keeping their seed phrases so secret that they can't find them themselves many years later, or keeping them all over the place so that they are stolen or discarded by mistake.
Never mind the newbies, I myself have a small safe with backup seed phrases for all my hardware wallets, written down on cards that come with the hardware wallet manufacturers, and I have dozens of these. One day one of my Ledger Nano S's broke, as we all know, the OLED burn-in problem, and I opened the safe and rummaged through a dozen or so cards with different seed phrases written on them, having absolutely no idea which one was the one I needed. The outrageous thing is that the cards didn't even have the Ledger logo on them, I had to use the process of elimination to get rid of those Trezor or Jade backup cards, yet it still didn't help much.
Imagine writing down the name of each wallet in a small notebook, with the corresponding seed phrase below in ciphertext, and then keeping a copy of the CipherCard in your safe with the rules for substitution encryption written on the back of the copy.
You could even keep a picture of the CipherCard in Gmail's drafts folder, the rules in Outlook's drafts folder, and the ciphertext of the seed phrases in the drafts folder of all your email services, and then use another CipherCard to manage the passwords for all your mailboxes.
Doesn't that make sense?
A little bit off-topic, but do you feel confident that having your seed phrase in ciphertext is a wise choice? I think it's extremely unlikely that someone can steal your coins, but with a slight loss of memory, you might get locked out of your funds.