No!
I've been looking over the Wikipedia page on the List of earthquakes in Mexico. It definitely doesn't justify that claim. Here is what I can say:
On 9-7-2017, Mexico's second largest earthquake in recorded history, at magnitude 8.2, struck in Chiapas in southern Mexico.
On 9-7-2021, a 7.0 magnitude earthquake struck in the state of Guerrero, which is close to Mexico City. This is the 71st more powerful in Mexico's recorded history
On 9-19-1985, Mexico's fifth largest earthquake in recorded history, at magnitude 8.0, struck in Mexico City and Michoacán.
If I look at the 30 most recent Mexican earthquakes on the list, I can say that 9 of the did happen in September. The probability of 9 or more in a September is 1 in 2031. However, the probability of 9 or more in any month, in the top 30, is about 1 in 169. The bottom line is I don't see anything very unusual here.