One more thing: while I know speculating about editing errors in a BTB rules discussion is highly frowned upon, while looking at the DMG combat example just now it stood out to me that if we take party A's actions in round one and move them to round two a couple of things make a little better sense.
As the example reads in the printed text:
Party A wins 2 segments of surprise:
Party A acts in surprise segment 1 (Arlanni shoots at Blastum, Aggro hits Balto, Arkayn casts Command on Gutboy Barrelhouse, Abner casts Magic Missile and hits Gutboy Barrelhouse)
Party A acts in surprise segment 2 (Arlanni switches weapons, Aggro loses his action (due to Balto's high Dex), Arkayn switches weapons, Abner prepares a scroll)
Round one - Party B wins initiative:
Party B acts (Balto attacks Aggro, Gutboy Barrelhouse and Barjin hit Arkayn, Blastum casts Shocking Grasp and kills Arlanni)
Party A acts (Aggro hits and kills Balto, Arkayn attacks Gutboy Barrelhouse, Abner casts Web, catching Gutboy, Barjin, Blastum, and Arkayn - combat ends)
However, if we change it to:
Round one - Party A wins 2 segments of surprise:
Party A acts in surprise segment 1 (Arlanni shoots at Blastum, Aggro hits Balto, Arkayn casts Command on Gutboy Barrelhouse, Abner casts Magic Missile and hits Gutboy Barrelhouse)
Party A acts in surprise segment 2 (Arlanni switches weapons, Aggro loses his action (due to Balto's high Dex), Arkayn switches weapons, Abner prepares a scroll)
Party B acts (Balto attacks Aggro, Gutboy Barrelhouse and Barjin hit Arkayn, Blastum casts Shocking Grasp and kills Arlanni)
Round two - Party A wins initiative:
Party A acts (Aggro hits and kills Balto, Arkayn attacks Gutboy Barrelhouse, Abner casts Web and catches Gutboy, Barjin, Blastum, and Arkayn - combat ends)
That would resolve a couple of anomalies - the fact that Abner's combat-ending Web spell is stated to have ruined Blastum's in-preparation spell (which makes no sense in the published text), and the mention in the postscript that this example covered "two rounds of combat" (when as-published it only covers one).
It's possible that the example was written in the latter way but then (sloppily) edited into the former. Since we don't know who made that editing call (or, for that matter, who wrote the text - IIRC this has been speculated as one of the passages that Gary farmed out to Lawrence Schick or Jean Wells*) that wouldn't necessarily tell us anything about intent even if we could confirm this is what happened, but would perhaps suggest that there was confusion even internally at TSR about how these things were supposed to work...
*
EGG in Dragon #25 wrote: TSR’s new Design Department, namely Lawrence Shick and Jean Wells, undertook the authorship of two sections — ostensibly to test the mettle of these good folk, but actually to assure that the whole manuscript would be finished in a timely manner.