Yes, that's all correct. TurboTax for 2018 cannot recompute your 2017 tax. You would have to do it yourself using 2017 TurboTax, or whatever software you used for 2017. There was a screen in the interview about your state refund that asked you whether you wanted to recalculate your 2017 tax return. You must have answered that you did not want to do it, and that's why TurboTax checked the box in the smart worksheet.
(The screens in TurboTax say that you could recalculate your 2017 tax manually on paper forms instead of using software. I don't think that's realistic, especially with AMT involved. And when you get into the details of the recalculation you find that in some cases you might have to do it multiple times.)
If you want to be able to check your tax return in this much depth, I think you would be happier with the CD/Download TurboTax software instead of TurboTax Online. The CD/Download software has a forms mode that lets you look at the actual forms and worksheets while you are working on your return, and even make entries directly on the forms. It also has features to trace where an amount on a form comes from. (These features are more limited on the Mac than in Windows.) You can switch back and forth between the interview and forms mode. The 2017 CD/Download software has a worksheet specifically for recomputing your 2017 tax to compute the recovery exclusion for 2018, and the 2018 CD/Download software has the same worksheet to do the computation for 2019. That worksheet is only available in forms mode. You should consider switching to the CD/Download software next year, even if you don't have AMT, itemized deductions, and a state refund in 2018. If you do switch, keep in mind that if you don't use TurboTax Online for 2019 you will lose access to any saved online returns from prior years. So you should download the PDFs and .tax20xx files of any prior-year returns and save them on your computer before October 15 this year.
