State tax filing

Follow-up:  on examining my 2018 NY State return as filed and comparing it with Turbotax's amended return I discovered that initially Turbotax did not add spouse's pension and annuity income exclusion to New York subtractions.  So now I will file an amended return.

The question is:  if Turbotax belatedly recalculated my NYS 2018 tax return, why was I not informed?  Why was this subtraction not found in the first instance?

This leaves me disappointed with Turbotax, and will make me concerned going forward on using Turbotax for more of my returns.