How would that system deal with spells that are not normally initial for Rydia (speaking of monster/enemy spells)? Remember she starts with 3 different lists....
I think it's a little more fuzzy that what you're saying...
This list is based off FF4's internal listing...
0E FF FF FF FF 35 FF 0F 03 04 12 13 16 FF 1D 20 23 2C 2E FF 0E 01 0D 07 17 FF 1D 20 23 29 1C FF 0E 01 0D 07 17 FF 01 .. 30 42
The stuff in bold are the terminators, the last value in italic is not separated due to a filled spell list.. however, the list doesn't read that way you say it is...
First spell is Cecil's (though, I wonder if that's inserted as a DK or Paladin), followed by Rydia's.. but it has
three preceding terminators instead of 2 (for White and Black magic).. which has some wondering if Kain was supposed to have a spell list.. anyways, that's followed by Tellah's White Magic, then Black Magic.. then Rosa's White Magic (most likely), then Palom's Black Magic, then Porom's White Magic, then FuSoYa's entire spell list, then Edge's only initial Ninja spell.
It could not possibly be that FuSoYa is ahead of Edge in the character ID order.

Similar stuff occurs with the spell learning lists.. at least in regards to the format... the terminator that comes from the middle of nowhere really makes it all the more confusing at times.