Now that we are in the 2nd year of the new tax code, I agree that this should have been addressed a little further. Between the high CT income and property taxes, my state tax bill easily clears the $10,000 limit. If I had over-payed the state in 2019 and was owed a refund, I would have been taxed on it even though this amount was already excluded from the 2019 tax deduction, so it is being taxed a 2nd time. However since I owed the state at 2019 tax time, I do not get to deduct the additional taxes because it exceeds the $10K tax deduction limit for 2020.
After further research, it appears there is some consideration for this. The following web page explains it well. Scroll down to the POP QUIZ near the bottom.
https://www.thetaxinstitute.com/insights/state-and-local-taxation/state-tax-refunds-tax-benefit-rule...
