Too soon to say whether Arsenal is going to win the title or not. They are in first place in the table and in the next week they will play against Leeds which is an easy game for Arteta and his players because they already won the last game they had against Leeds this season, also during the last games they had, Leed couldn't perform well enough while Arsenal got almost every possible point.
Maybe your statement is right that it's too soon to say Arsenal already won the league championship this season because there are still many possibilities for it to happen, but if they fail won't it be a big failure? and maybe they will get ridicule from many people even from City fans who are their competitors. Let's assume City won 1 game they haven't played means the point difference with Arsenal is only 5 and to catch up they will expect Arsenal to lose 2x in the remaining 10 matches and City win all the matches and I feel that is impossible to happen where Arsenal let the trophy that is in sight fail them lift for failure at the end of the season, it's not comfortable if our fate is determined by other parties and City's fate is really determined by Arsenal's performance.
One of the important matches that City will play is this Saturday. We'll see if City fail to get 3 points, then Arsenal will benefit even more if they keep the chance to get 3 points safely by beating Leeds.