Quick writeup for where this glitch is pulling its techs from:

(I suggest watching / reading the description of if you just want to perform the glitch for the first time)

Whenever you open the Techs menu in general, the game calculates the list of techs to show for every character at once (not just the one you have selected) and stores them into memory.

More technical details: For PC, with TSFix, these are stored at TOS.exe+70dde4 onwards. 72 bytes per character which gives room for 36 2-byte tech indices, though no legitimate techs go anywhere near needing the high byte. They're stored in the same order that your party is currently in, so TOS.exe+70dde4 is the first tech for the character in slot 1. Old values are NOT explicitly erased, only overwritten by new ones.

So when we use the glitch to make the cursor go to 0 and then negative values, what we actually do is access values from before our current character's list. Provided our current character isn't in slot 1, the first few values will come from the lists of the characters immediately above them in the party. 0 to -35 is the slot immediately above, -36 to -71 is 2 slots above, and so on. Anything that goes past the rest of the party above your current character is essentially junk data which contains almost no usable values, mainly just a bunch of 00s. In theory a TAS could maybe abuse one of the constantly changing values to get an MA early, but none of it looks usable in RTA.

To get an MA, we need to have another character in the party who knows the move whose index number is equal to the MA we want on the character we're looking from. An example is Lloyd's Falcon's Crest, which has index number 21 (hex) / 33 (decimal). The only other characters with moves with indices that high are actually Genis and Sheena. For them, index 21 is Force Field and Summon: Darkness respectively. So if we use the MA glitch with Lloyd below Genis, and Genis has learned Force Field (which he is guaranteed to do at the Fire Seal) then we can grab Falcon's Crest.

Full list of move indices for the PC version: https://docs.google.com/spreadsheets/d/e/2PACX-1vRML9wnCTdGwl61i-WK3rTSEg_qnA-lNoNnkhOcri0j9-z-ZCjszC9wdEDFhHO_i0QjBAqtEHmFz1A6/pubhtml

Takeaways from this for the speedrun:

• At least for NG, all our MA glitch setups are 100% stable, provided the character we're getting the MA for can actually activate the glitch. To be able to do so, they need to have 7 moves. This is only ever a problem for Lloyd (needs to be Lv14 to make Beast appear in blue as his 7th move) and Presea (needs to be Lv33 for Resolute Infliction as 7th move) so those are the only deaths that can mess up our route using the MA glitches. All the base moves are guaranteed (Genis Force Field, Colette Sacrifice and Judgment, Sheena T.Seal Lightning and Summon: Earth) or essentially so (Raine Inspect Magic, which is a Lv20 move that is only needed when Presea hits Lv33)
• For PC Symphonia speedruns we will have to enforce a rule where the game has to be restarted before each attempt. This is because of a detail I mentioned earlier - "Old values are NOT explicitly erased, only overwritten by new ones". This fact would mean that you could load a file with advantageous MA glitch tech positions before starting your run, and then get MAs super early because your much shorter tech lists in the run itself would not overwrite the ones from the old file if they were far down enough.