TSL didn't sell as well and was less popular critically than KotOR. Which may be part of the reason that LA and Bio have rather glossed over it.
What's more interesting is why Bioware have glossed over the Mandalorian Wars in their video-promo-things, which was their own invention. Maybe they're playing with unreliable narrators, but if so it's something of a deviation from type for them.
I'm not a fan of mandalorians, but retconning the Mando Wars just doesn't seem to make much sense.