Turtle Charm/The Wailing Wall Clarification

Specifically the line

"

Can Block Damage from all Hits while Shield is not Raised

or

"

Can Block damage from all Hits

Does "all" just mean aoe damage? Does this include unblockable attacks from bosses?
This doesn't seem to work with self damage (e.g. Heartbound Loop/infernal flame/Fireflower) and I'm fairly sure this also counts as a hit, as i think other effects like recoup would work