There is a rubric on Page 18 of the BCP2019, Morning Office, that reads "The following verses may be omitted" right in the middle of Te deum. Am not aware of when, or why, this would traditionally be done. Is this for penitential days? Or some other occasion? Thank you for any and all input.
It would be good if the user known as DivineOfficeNerd was still posting. He knows the members of the liturgical taskforce and could find the answer if he didn't know it. I wouldn't be surprised if it's just a concession to shorten the service to some arbitrary length that was thought to be better suited to the American (lack of) attention span.
The hunch that I'm getting is maybe the whole thing is to be said on Sundays, with the canticle abbreviated on weekdays through Christmastide.
I still lurk! The last optional verses are considered a later addition to the text. The 1979 BCP placed them as an alternate version of the suffrages, and omitted them from the Te deum proper. The 2019 BCP adds them back, though with the provision that they may be omitted (to respect the received tradition of most of the ACNA world, which used the 1979 and didn't have those verses at the conclusion of the canticle). Hopefully that helps!