Given what J. K. Rowling has said about the fantasy genre (she doesn't like and doesn't read it) Rowling probably never read Le Guin, certainly not before she wrote Harry Potter.
You can kind of detect "doesn't even know they are plagiarising". I've seen it in some stuff by Michael Creighton (Doctor Who) and Robert Harris (X-Files).
I guess in the geek bubble it's quite easy to assume everyone is intimately familiar with Earthsea, Doctor Who and the X-Files...
The thing is, no-one was zinging JKR for being unoriginal on release, at all. On the contrary, people were saying the opposite as noted. Sure that was irrational, but it wasn't like fantasy authors were wading in to critique her. Indeed, the few fantasy authors I saw discuss her work at the dawn of Pottermania were pretty positive and excited that a new voice was getting fantasy noticed, and not picky about it.
It was JKR who did repeated bizarre interviews where she really rude about fantasy as a genre and asserted she was totally original. The interviewers were often at least somewhat familiar with fantasy, and would try to be positive and put JKR's work in a context of fantasy, in a good way, and she'd be like "NO!!! THIS IS NOT FANTASY! Fantasy is dumb stuff for dumb teenage nerd-boys!" (and yeah pretty much that vehement - I used to have a link to an interview from like 1999 or 2000 which just like
blistering...). Always kind of funny given Harry is totally a teenage nerd-boy that teenage nerd-boys loved.
So eventually all the trash JKR had been talking got back to Le Guin and Le Guin was, rightfully, unimpressed. She's a lot more polite than I'd have been!
See also: That time the NYT's main TV reviewer (not entirely dissimilar to JKR in personality/background) saw the first episode of GoT and decided to explain, in her review, that all fantasy (including GoT) was dumb stuff for teenage boys, and the no self-respecting woman had any time for. Great work New York Times lol.