The item description is wrong for pure good burst, the pure good burst part does NOT do 1d6 Pure Good Damage per hit, and the burst portion of it IS pure good damage, not holy so it works on all non good mobs.
So in the end you've crafted a +5 holy burst where the burst potion is pure good so it works on non-good mobs.
e.g. On a an evil mob it will be +5 holy burst, on neutral mob it will be +5 weapon, 4d6 Pure Good damage on crits (for a khop).
(Combat): Your weapon's good burst effect hit Twilight Giant Rat for 13 points of good damage.
(Combat): Your weapon's holy effect hit Fiend-Blood Troll for 9 points of good damage.
(Combat): Your weapon's good burst effect hit Fiend-Blood Troll for 10 points of good damage.
Be warned, don't craft these items if you expected a +5 holy burst of pure good (effectively)