No . . . the order went . . .
Commanders on the same side bid between themselves for the right to lead the attack. You can see this when Phelan is with Ranna watching the bidding and Ranna finds out her star has been cut from the bid. Similarly when Natasha is bidding against Star Colonel Marcos, and she just randomly cuts stars driving it down to give him heartburn. Then asks if that is it, you know to avoid wasting time. Then she said her final bid is- 'One.' Marcos pulls out his remaining hair asking what?! One Trinary, One Binary, One Star?? One warrior, and only one warrior. We see the Jags bid among themselves, with some never seen before bits about knives/stars, to see who gets to hit the Highlanders that land on Wayside. Plus other incidents. They already know what the defenders will be by this point since information among the Clans was never hidden and during the Invasion ComStar was providing up to date info for numbers.
The winning commander contacts saying they are attacking with 'Two Trinaries of the 4th Wolf Guards Cluster' what do you defend with? They typically transmit the unit histories and codexes at the time- the codex does not say what you pilot, its a dossier & genetic information. A codex will state when you left the sibko, how well you did in your Trial of Position, any combat since, Bloodname prospects MAYBE, and who your geneparents were for the iron womb. Unit history will simply be a list of engagements (check battle streamers on unit flags for an idea) . . . for example, my old unit? Chased Pancho Villa, involved in WWI, WWII in Sicily, Italy and France, and Rhineland (we freed Dauchau- the unit museum talks about the conditions and displays trooper's records), to Korea in '51, Desert Storm where we won recognition that pissed off the regulars for at least 20 years (basically until they retired), Iraq round II, Iraq patrol x2, and Afghanistan. The point of the unit histories is to make your victory mean something because you face a storied opponent. Facing the 4th Wolf Guards is a bigger deal than facing the 11th Wolf Regulars, simply because the Guards won that title through their service. Facing a SLDF vintage unit, like the 328th Assault Cluster, is a bigger deal than facing a Falcon Eyrie cluster- and I say that as more than the Falcon v Wolf rivalry.
None of that says Mechwarrior Pierre plans to pilot a Gargoyle D in the fight rather than a Gargoyle Prime. Now, while the Wolves would not say Pierre has a Gargoyle the unsecured nature of the information the Clans share means before the Invasion most of the Clans will know a unit's equipment composition since the information is wide open. Mechwarrior Pierre's codex WILL say he is from Trinary Assault in the 4th Wolf Guards, but its not going to say he drives a Gargoyle.
Once the defenders knew what unit was attacking and objectives, along with the information sent they would either have a immediate response (sometimes in fiction) though more likely they said "BRB" if they were going to defend with less than everything. Which is where the defendering commander bid among themselves to defend the target of the Trial. This does happen in several fiction/SB sources as well.