[Chaos]

"Slow" was an effect that reduced your Movement by LV, if I recall correctly. It never touched CEL or anything else that Cripple Leg would've caused beyond movement impairment. Celsius Shell's charge effect is the only clear Slow effect that I'm currently aware of.

In which case, unless we're going to say that Lingering Damage is close enough to Burn to count, I'd believe the difference between "Slow" and "Cripple Leg" is enough to drive a difference between the two.