He may have been able to get some burnt as a third-string PG in the 30-odd games as a that Parker was still out, but that quickly would've dried up.
Players develop by playing, and he was able to do that a lot more leading the Austin Spurs. That was way more valuable to his development, even at a lower level of compe ion, that getting 5-10 garbage minutes a game ever would have been. The only other option would have been fitting him minutes at the 2, but playing out of position doesn't help him play to his strengths either.
That said...I want Parker out and want White firmly entrenched in the rotation next season.