To a rules officianado guy...
 

What's the logic here? Lineup cards and rosters.

Why do we emphasize turning in a correct lineup card and have the coach double check it before it's accepted only to find out later in the game he forgot to write a name down as a substitute.

We now "forget" the official lineup card and allow him to "add" a player as long as they are on the roster.

This sort of make the "official approved lineup" mute if it can be changed.

I'm of the school, that what you turn in is what you use once you've been given a chance to double check it for accuracy.

What's the logic of allowing modifications to lineup cards after approval?

The content is official with regard to starting, sequence, position, etc. Adding players later does not change those aspects.

What's the logic of using the word mute instead of moot? :D

Agreed, but whether players can be added to the substitution list and the consequences vary a bit with the rule set. In high school, for example, corrections can be made once, but they come with a warning. After that, the coach is restricted.

Besides, my line up cards never speak anyway. ;)

Because I didn't want to hear a spelling correction about using the wrong spelling of moot, so I said mute......and yer buy'n that I'm sure.

Because an eligible player doesn't lose eligibility simply because their name is not listed as a possible substitute.

Don't confuse the line-up card with the line-up. While the line-up card is the official document, the line-up is with what we are concerned.

Subs aren't in the lineup. That's why they're subs.