No, Sammy did not choose to be the first wave. That was Charlie's choice. Because Charlie is angry.
We know that at one point, GK was taking their turn. GK uses their veil trick to capture Ossomer, and gunk Tramennis. On the same turn (Tramennis is still gunked) Wanda moved forward to make parley, and GK's turn was ended and RCC's began. Jillian moves to meet Tramennis, and Charlie talks to her on the way. At this point, Charlie has a "situation," goes quiet for several minutes, then disconnects abruptly.
At another point, Charlie's scouting team took their turn at dawn, because they were unallied. Charlie is blacked out at that point, *and has been since the day before*. Then RCC's turn begins, including Haggar's Sammy discovers them, Sammy has his conversation with Charlie, who is no longer blacked out. Haggar then moves to meet Tramennis and Jillian.
There's a couple things that get me about this, though. First: Charlie was blacked out at least one turn BEFORE Kingsworld. But why? We know that Vanna was linked with Charlie, since Charlie 'released her', but how long? Why the black out since the day BEFORE, rather than beginning the link at dawn? Why did Charlie spend his entire turn on this day blacked out?
Then there was the developing situation:
Then she heard Charlie's voice, for the first time sounding stressed. "That's extremely interesting information, Jillian. We'll talk about it later, but I've got a developing situation. Please don't attack the column alone. I'll try to get you some help. Goodbye."
We assumed at the time that the developing situation WAS the information about Wanda, but that didn't really fit the sentence. Charlie is usually very eloquent. My suspicion, now, is that that conversation was happening at the same time as his scouting stack was being attacked by Haggar. He sounded stressed because he had just found out that his archons were being killed. He terminated abruptly because he needed to talk to Sammy. That answers the question about whether Charlie can hold two conversations at once. He cannot.
What's key here is Charlie's actions. We have NEVER seen Charlie as anything other than cool and in charge. Except once- to Jillian. For the first time, sounding stressed. Charlie has never come across as anything but level, even at the height of TBFGK. He has never been terse or stressed. And then he orders Haggar's army into a "first wave" attack against GK's infantry. First means that it won't be enough- which means, likely, that Charlie expects very high casualties. For Haggar.
Charlie is PISSED about the loss of his archons. The only motivation we've ever gotten from Charlie- indeed the only motivation even his archons are aware of- IS his fleet of archons. Those archons have not merely loyalty and duty, but something approaching love. My off the wall idea is that Charlie feels pretty much the same thing back. And then the bonus is this. If Charlie is that pissed off at Haggar for killing three of his precious girls... just how furious is he with GK and Parson, for not merely killing but STEALING them?
(And my tinfoil theory: Archons have thinkamancy AND foolamancy. They have a natural thinkamancy network- something like a hive mind. The ONLY units Charlescomm appears to have are archons. The only motivations Charlescomm appears to have are cash, and that only for increasing their numbers. That sounds an awful, awful lot.. like a natural side. Like the hobgobwins. Does Charlie even exist? Or is Charlie the chief archon?)