Accounting for recency, the claim for best leaves much to be desired. But to be specific, Damwon is one of the three "new era" teams that took LCK by storm alongside Griffin and Sandbox. Where the notion of best team accounts for is their consistent discussion of being top of the table in a parity driven LCK season.
The keyword here however is "parity." Yes it cannot be ignored of their fallout in the summer playoffs, but "barely beating KZ" shouldn't support the claim as to why they wouldn't be considered a contender. Damwon has incredible skill ceilings per player. But like the other Korean reps including SKT, they harbor a vulnerability that with the right mentality by opponents, they'll flop.
Information aside, who the hell is saying Damwon #1 and isn't being just a wee bit delusional or overconfident?