*nods*
Especially since the two examples are on a whole different level of importance too - writing around Blaise's skin colour and the bit of history we have on him takes a handful of one-liners at most in an existing WiP (well, unless the writer has created an elaborate family background for him that carries the whole story). Writing Snape out of a member of the pureblood wizarding aristocracy plotline can pose a much greater problem for a story.

Though I'm not bemoaning the explosion of Snape Manor in fandom (she says, busy trying to eradicate the term 'Malfoy Manor' from her vocabulary).