In the documentation, it says the tags BONUS:STAT|BASESPELLSTAT;Class=X and BONUS:STAT|BASESPELLKNOWNSTAT;Class=X add to the character's base spell stat bonus, when in practice they seem to add to the character's base spell stat score.
I assume the same is true for the non-class versions, but I haven't tried it.
I'm not seeing this when I check 6.02.1.
I created a 1st level Halfling Sorcerer with 15 in everything except Chrisma where he had an 18. These are prior to adding racial bonuses so final stats are S:13, D:17, C:17, I:15, W:15, Ch:20.
With the Sorecer's Archetype "Crossblooded" and Bloodline "Sage" the stats remain as shown above but the Spell Bonus is granted based upon the INT instead of CHA. The Bonus is effected, not the actual stat.
If you look at how the Sage Bloodline is coded up, there are copious references to INTSCORE and CHASCORE. The tags add/change the spell stat score, which it should in order to get the highest spell level known correct. But the tags say they add to the base spell stat bonus, which doesn't really make sense in this context.