I don't think anyone has suggested the ability to magically heal extreme consequences. At best, consistently-applied therapeutic biomancy MIGHT be able to allow a full recovery from such wounds (provided that recovery is even remotely possible) in a manner similar to Wizard's Constitution allowing Harry to keep his hand, but that's about it. Also, death is not an Extreme consequence;death is a Taken Out consequence.
The problem stemming from these contradictory rules is that it is hard to know where the "wiggle-room" is in terms of Biomancy. Reiki is allowed by default because it's a sample spell in the bloody book, but when it comes to creating new/different healing spells... what can you do?
For example, say I want a spell that can temporarily suppress the pain and disability presented by a given physical consequence. The drawback is that the injury's recovery time is increased by at least double, or more depending on how long the suppression lasted. So, using this spell to clear out a severe consequence would increase the recovery time to at least two full scenarios, but would give the PC the ability to stay in the fight for as long as the spell lasted, possibly meaning the difference between succeeding or failing at that scenario. Only one consequence of a given severity can be suppressed at any one time. The inspiration for this idea comes from the bracelet of stones McCoy gave Dresden to temporarily suppress the pain in his hand, which would have been excruciating otherwise. As the dust settled, the last of the stones shattered and the pain came back. Is this sort of spell allowed with biomancy?