Those criticisms aren't about mere bugs, but a bloated over-engineered iOS apps with far too many classes (18k back in 2015) [0]. The Android app was also previously notorious for patching Dalvik at runtime to deal with the huge number of Java methods [1].
Granted, perhaps things have gotten better in the last five years.
It's certainly possible for an enormous engineering company to have poor code quality or poor engineering practices, despite having a high interviewing standard. And a criticism of Facebook need not be a criticism of all companies that interview by Leetcode, for instance no one here is criticizing Google, Amazon, or Apple, and all have better reputations for code quality.
