According the the ELO instructions "You can only challenge an ELO player with an ELO value between -50 and +150 of your ELO value.", but when I try to challenge anyone it always comes up with various errors: "opponent deck not valid", "opponent banned", "unknown error", "you can't challenge in this room". So how do I challenge a player with +150 ELO?
I any pairwise match A has to equal B, otherwise it can't be pairwise. Since "Fight Now" creates a pairwise match the statement in the instructions is Logically impossible. Therefor it is inaccurate. Systematically you can not actually "challenge" anyone, so the sentence is incorrect even before it gets to the specifics of who you can "challenge". My guess would be that they had originally intended people to be able to challenge other players in ELO, but decided to remove that feature for gameplay reasons and forgot to remove the line from the instructions.
"challenge" is basically a random match vs a player that falls within the point +/- spread. no need to talk about coding
maybe something got lost in translation to english.
or if we can into semantics one might interpret challenge as an open challenge to anyone that falls within the point spread