I wouldn't rule it out too quickly. The John and Mary Sarley in Chicago in 1930 and 1940 are definitely the same people who are in Crawford Co., KS in 1920 (same occupation, and the informant on Mary's death record has the same name as the stepson in the 1920.
So the question is whether John Sarley with Mary and stepson in 1920 is the same person as John Sarley with Anna in 1915. If they're different, it means that one John Sarley disappeared and was replaced with a different John Sarley with the same approximate birth year and immigration date and in the same county. Seems unlikely though not impossible.
A search for either an Anna death record or a John remarriage record during that 1915-20 period could help confirm that.