The Bonus Spells Known Per level for Sorcerers were set before Lesser Animation of Po existed.
I feel that Lesser Animation would be a thematic and useful L4 spell, for 2 perks that have thematic but underwhelming spells.
Necromancer life isn't easy. Carrion Feaster and Rotbringer's L4 spells might be Necromancy, but they don't really combine with what the perk is about.
Giving them the new spell that leans into 'animate the dead' seems like a good change, as then they have a Backup Undead for if their Horde gets wrecked.
Carrion Feaster has Contagion, a spell that does essentially nothing to monsters or PCs. Disease is easy to remove and won't do anything mid-fight.
Rotbringer has Fear. A spell that bounces off the many, many Mind-immune monsters. And is weak vs PCs, because Fear Save bonuses are common and Remove Fear is cheap.
Bone Warden is fine as it is.Stoneskin is just good for everyone and it gets an additional 'send more skeletons' summoning power.