A lot of philosophy departments are very poor[1] (nothing surprising here, a lot of CS departments are also very poor).
On top of that, it seems to me that, at least outside the most prestigious schools (e.g. Ivy's), philosophy departments at schools with respected CS programs, are even less likely to be high quality. This is exacerbated when you compare the quality of the CS program to the quality of the philosophy program, since we are already talking about schools with quality CS programs.
This means that the average HNer likely went to a school where the quality of the philosophy department is much lower than the CS department. So when an HNer says "A philosophy education sucks" they really mean "A poor philosophy education is worse than a quality CS education"
This is exacerbated by the fact that the first several philosophy courses one might take typically focus on gaining a groundwork in philosophy. It's not unlike someone finishing elementary school thinking math is just boring arithmetic.
At the school I went to, the smartest student in a philosophy class was typically an engineering dropout, and the intellectual rigor of the classes was poor because they weren't allowed to fail 50% of the students (unlike engineering, where that fraction would be high, but not eyebrow raising). For most of the time I was an undergrad, I thought that all philosophy majors were less intelligent than STEM majors and philosophy was not at all intellectually rigorous.
1: When I say "poor" I am being a bit vague, but consider it a qualitative mix of the faculty, curriculum, and students. Of course these 3 things are very closely interrelated as curriculum difficulty is adjusted to the level of the students, faculty has some control over the curriculum, and having quality faculty and curriculum will attract better students.