Ever wondered what Genis' Compound EX Skill "Magic Boost" does? Allow me to explain!

Chapters:
0:00 Preamble
0:21 Hypothesis
0:34 Battle with Magic Boost
2:33 Battle without Magic Boost
4:31 Conclusion

tl:dr: Magic Boost allows spells to deal Critical Damage

Update: After some extra testing, I can confirm Attack Symbols do factor into the spell's critical chance.
You can see the testing here if you like (it's just me spamming Air Thrust for 25 minutes): https://youtube.com/live/8GxD-WDqzJ0
With 2 attack symbols: 569 Hits, 135 Crits, ~24%
No attack symbols: 469 Hits, 16 Crits, ~3%
Efreet rolled damn high on his luck for that fight xD