I don't think they are actively discriminating. Non-native accents are generally harder to understand, even for people. This is more or less true depending on the what kind of accent it is and how heavy it is.

I'm sure if a voice assistant was developed in Japan and I tried to speak Japanese to it with my American accent, I would have a really hard time. I wouldn't view this as discrimination, I'd view it as my Japanese being hard to understand.

I have issues with Siri trying to set a timer for 50 minutes. It always thinks I say 15. This isn't a hallucination, it's a misunderstanding, as the two words sounds very similar. Humans can also make this mistake and generally will ask for clarification if the number doesn't make sense in context. The typical way to clear this up with a human is by saying "five zero", which is what I started doing with Siri and it works. To be fair, 15 is a much more normal and common timer length than 50.