They don’t need to send the same signal inverted, just allow both cables to react in the same way to any interference (maintain the same impedance).
These are both the same thing, just viewed from different angles. Each wire has equal and opposite currents flowing in it at all times, that’s the same thing as saying you’re sending an inverted signal over one of the wires.
“phantom power” […] “bias power”
Stage audio almost universally uses “phantom power” to mean 48V balanced, which is a nice standard meaning for the term, but I’d never claim someone is wrong for claiming they are doing balanced signals + “bias power”. It’d raise an eyebrow (have they made a mistake? it’s uncommon) but it’s still reasonable, I don’t think “bias power” specifically refers to only unbalanced configurations.
Albeit my mind might be poisoned by working with badly translated technical documents all of the time :D