if you dash through a rolling cactus, stationary or otherwise, you will take ludicrous amounts of damage and instantly die.
i do not know if this applies to all boulder-type objects, i have not tested.

the same also happens when dashing through steam geysers (from calamity mod).

if i had to guess id say the high damage is probably a result of the speed you're moving at.

but in any case the 'intangible' part clearly doesnt apply to some things and id say that is another, separate bug.