Vidas clearly remembered his elders telling him that humans were the most shameless of all in Anril before he left Emerald Forest. Hence, he had to think of a way not to let the human go back on his word.
"Castellan Arathor, please help us arrange a suitable place to begin the battle. On top of that, Mage Felic, I hope to let the audience witnesses our battle. So, why don't we allow them to be the spectators of our bet?" Vidas knew that apart from having poor integrity, humans also placed great emphasis on their pride. Hence, if there were lots of spectators, he wouldn't have to worry about Lin Li going back on his word.
Actually, the elves were not the only race that saw humans as sly and scheming beings. Even the demons who often tempted humans into selling their souls racked their brains for the sake of the soul contract because they did not want to let humans take advantage of them.