Best I can tell, people liked Spalter for the low-risk clears of the main map, but the deployment limit risks likely discourage using her for higher risks. She is good for a fixed stall duration while others dump more damage on the boss, but I'm among other people that opted for the infinite Hoshiguma stall for the risk 18 clear. Horn saw basically no support use early on so likely she was either called in for evolving main map strats or leaned on to break some of the daily map challenges. Lappland is too busy being sad that no one picked her to bother showing up on this screen, though I don't think she was going to be swinging hard in this CC regardless. It might have been better to have Specter Classic in the 5* support slot for this event.
I'm kinda sad I showed up to Arknights late enough that I could only meaningfully participate in CCs 11 and 12. There is a charm to solving most of these challenges, even if some of them felt miserable to engage with (the Ch. 10 artillery cannon is probably still my least liked map mechanic). Hopefully HG finds a way to continue the intent of Contingency Contract in whatever new nonsense form they come up with.