After applying the damage multiplier, Dripstone converts the falling damage into basic physical damage, which is not affected by Feather Falling, but is instead blocked by armour/Protection enchantment. That makes you able to fall far greater distances if you fall on a dripstone with good armour, much greater than when falling on land.
For instance, Netherite Protection IV Feather Falling IV gear allows to survive approximately 98 blocks of normal falling OR above 200 blocks of falling on a dripstone. That does not make sense at all.

Steps to replicate.

Prepare a set of Netherite armour with Protection IV and Feather Falling IV. Lift yourself 98 blocks above a Stalagmite, then jump on it. After this remove the dripstone block and do it again.

Expected behavior:

Landing on a Dripstone does more damage and neither of the falls damage armour.

Observed behavior:

Falling on normal blocks deals 18-20 points of damage, falling on a Dripstone deals around 8 and reduces armour durability.