Fans talk smack and look for nefarious plots by their opponents. Grass fields require regular watering; there is anecdotal evidence available for "watering the field before the game" for every grass field that ever existed.
Mix those two ingredients and there are anecdotal stories in every fan base.
By thew way, did you know that grass fields are regularly mowed... There are anecdotal stories in every fan base about opponents keeping the grass longer on purpose.
Some of the stories are true. Most are just fans being fans.