stop when call is not from "aov()" or "lm()" in R?

I have an R function programmed to stop when input is not a call from "aov()" or "lm()".

Below, I expect when using fit3 as input for my function to stop, but I'm wondering why it does not?

P.S. The function correctly stops when fed fit4 but doesn't stop when fed fit3; WHY?

fit2 <- aov(mpg ~ wt, data = mtcars)
library(rstanarm)  
fit3 <- stan_glm(mpg ~ wt, data = mtcars) # This call is from "rstanarm" package !!
fit4 <- glm(vs~mpg, data = mtcars)


bb <- function(fit = NA){

  if(!(any(is.na(fit)))){  

if(fit$call[1] != "lm()" && fit$call[1] != "aov()") stop("Error")
  }
}
# Examples of use:
bb(fit = fit4) # stops as expected ! because call is not from "lm()" or "aov()"
bb(fit = fit3) # I expect the function to stop why it doesn't? !!!!