Remember that not all closing costs are allowable as adjustment to basis.
See publication 523 and 551,
https://www.irs.gov/pub/irs-pdf/p523.pdf
https://www.irs.gov/taxtopics/tc703
(You generally can't include an appraisal, for example.)
Turbotax does the walk-through because not everyone knows that some closing costs are allowable. You only have one basis, so if you are confident you can calculate it correctly (and you keep a record for as long as you own the home plus 3 years after you sell), you don't need to follow the walk-through, you can enter the basis as a single number.
