Detail Reporting Exception: if you summarize Category A or Category D, Form 8949 is not needed for transactions without adjustments. No mailing is necessary. No attachment is necessary.
Turbotax has started to suppress some of these transactions,
even though IRS gives you the option to detail them on Form 8949 directly.
This is an undocumented "feature" of TurboTax ;.
since it is undocumented, the actual algorithm is unknown.