I don't see much point in speculating at this point. The character easily could have had something like the Life Giver perk, which would throw off the ratio. We could also be dealing with a system like Skyrim's leveling, and you have to choose between increasing your health or AP when you level up.

*edit*

Screw all the math I had before

At https://youtu.be/D5esyZPt5Jo?t=17m53s, we can see a level 48 character with with 365 HP.

If we try to figure this with the 90HP, at 2endurance, and level 1, from the other part of E3 stuff, we get the following math.

HP = base + XE + lvlmulti*level

90 = base + 2E + lvlmulti*1

I am going to assume that base is 45, lvlmulti is 5, and endurance raises your HP by 20 points per level.

90 = 45 + 40 + 5

90 = 85 + 5

90 = 90

Now, if we use 48 in there, and assume the player has an endurance of 4 we get

365 = 45 + 80 + 240

365 = 125 + 240

365 = 365