It's rediculously easy to implement, which makes me think it has to do with some industry standard for a PG rating rather than laziness of the developers, as it literally means ~2 more lines of code to fix this.
But AFAIK, some of these words are allowed with PG. In movies, at least. I know rules differ between countries, though, and it can be confusing to draw a line. I've done a bit of forum moderating, and oh the arguments over whether a word is actually offensive and which words are MOST offensive, even between British or American English (there is a word that can be a woman's name in the US that is a fairly rude slang term for certain body parts in the UK), or regional differences within a country regarding which words are most offensive.
But note that in movies, words like classic, cumberland gap and so on would not be banned.
It could also be a matter of the squeaky wheel getting the oil, and if even a handful of people complain about a word like ClASSic, or if someone finds a "clever" way to name their zoo that uses a legitimate word in a not so "nice" way, they decide this is why none of us can have nice things.