at least they don't prevent firefox from supporting a 11 years old version.

The 3rd generation iPhone SE was released in 2022.

Both iPhone SE (3rd generation) [2022] and iPhone SE (2nd generation) [2020] support iOS 18.6.

So that commenter must not have those generations and your comment doesn't help.

iPhone SE (1st generation) [2016] is stuck on iOS 15 but still receiving security updates, like 15.8.4 from the spring.

the 2022 iPhone SE supports iOS 18