When looking at multiple eso sets with the common 400 damage increase for their fifth item, I noticed that Silks of the Sun set has Max Health instead of Spell Critical for its second item. So what I am wondering is why the difference for this set?

Silks of the Sun Set
(2 items) Adds 1206 Max Health
(3 items) Adds 1096 Max Magicka
(4 items) Adds 129 Spell Damage
(5 items) Adds 400 Spell Damage to your Flame Damage abilities.

Ysgramor's Birthright Set
(2 items) Adds 833 Spell Critical
(3 items) Adds 1096 Max Magicka
(4 items) Adds 129 Spell Damage
(5 items) Adds 400 Spell Damage to your Cold Damage abilities.

Netch's Touch set
(2 items) Adds 833 Spell Critical
(3 items) Adds 1096 Max Magicka
(4 items) Adds 124 Spell Damage
(5 items) Adds 400 Spell Damage to your Shock Damage abilities.

Strength of the Automaton Set
(2 items) Adds 833 Weapon Critical
(3 items) Adds 1096 Max Stamina
(4 items) Adds 129 Weapon Damage
(5 items) Adds 400 Weapon Damage to your Physical Damage abilities.