If a particular box is not there, you can generally assume it was blank. Brokerages tend to produced a condensed 1099-B to save space: it would be very cumbersome parsing hundreds of pages of a full-IRS-layout 1099-B.

In practice, the condition for Exception 2 is "the 1099-B is already correct and you don't need to make further adjustments". Because if it isn't, you might as well fill out Form 8949.

It's definitely possible to have tax software summarize, although I suppose they might not do it by default.

https://ttlc.intuit.com/community/entering-importing/help/ho...