Correct - the TextVar is a text variable that is dynamic based on the context of the other message arguments. It can represent items (such as "Bicycle"), Pokemon, locations, etc.
Some examples:
06 1A 03 00 C2 01 - [it] saw [OT] using Bicycles. The Pokemon definitely remembers that it grinned.
04 30 09 00 46 00 - The Move Deleter that [it] met through [OT] made it forget Strength. The Pokemon remembers that it got nervous.
01 04 04 00 09 00 - [it] became [OT]'s friend when it arrived via Link Trade at... a Pokemon center. The Pokemon remembers that it got overwhelmed by emotion.
03 1A 01 00 5D 01 - [it] saw [OT] using TM22s. The Pokemon remembers that it had fun.
Short list of feelings observed (could be wrong in a few places):
0 it was happy
1 it had fun
2 it was glad
3 it grinned
4 it got overwhelmed by emotion
5 its feelings were indescribable
6 it felt good
7 it got teary eyed
8 it got lighthearted
9 it got nervous
A ?
B it was restless
C ?
D it felt sorry
E it felt emotional
F it felt nostalgic
10 ?
11 ?
12 ?
13 ?
14 they ended up in a foul mood.
15 ?
...