As usual, let’s start with what we know for sure. 7 of 8 rivals have 20 land tiles in their BFC, with a 1-tile lake adjacent to the capital. Spanish Poly, who settled on T0, have 21 land tiles in their BFC, and no water tiles.
In the Soldiers category, we know that overall Power went up by 2000 points (Average went up by 250, and 250*8 = 2000). This must have been a warrior build, but we don’t know who built it. It could not have been Poly or RB because Rival Best did not increase. We’ve been able to keep a close eye on which tiles Civfr have been working (FP T0-T2, Deer T3-T5), and it appears they have not yet produced enough hammers to complete a warrior. Also, since Civfr did not grow this turn, they are almost certainly building a worker.
So let’s look at everyone else. Everything from this point on is pure speculation, but I will rule out the Exp teams immediately (Civforum.de & Uciv), since their trait screams Worker First. That leaves WPC, Spanish Poly, and CivPlayers. The math seems to fit best if a team that settled on T1 has been building the warrior for 5 turns with 3 hammers per turn, so that means Spanish Poly is out. As for motivation, there are a couple things that might make a team want to start with a warrior, instead of the more obvious worker. The most logical would be going for a religion, and therefore not having the techs necessary for a worker to improve anything. Or maybe one of the teams that started with a scout is concerned about their undefended capital. This fits CivPlayers pretty well, since they start with a Scout and Myst. On the spreadsheet, I’m going to pencil them in for a warrior, but we’ll know for sure when a religion is founded or someone grows before anyone else (on T11-T13 if they don't go worker or settler next, depending on what tiles are worked from this point forward).
Edit: One other minor thing to mention, is that Rival Average Mfg went up from 2 to 3. This corresponds with all the teams that settled on T1 getting their border pops. This could be the Deer tile coming into play for all of them, increasing average Mfg without decreasing average food.