The process was exactly the same as everyone else has described—after replying, an instant reply from HR with a link to a hacker rank test. 90 minutes was allocated, but it was maybe a 30 minute problem tops. It sure didn't look like a senior level question.
After submitting it, there was radio silence until HR emailed me at 2am with the same generic response everyone else has gotten and a coupon for their services. No further follow up responses. It was weird.
Honestly? I wasn't that jazzed on the company after reading all the other negative reviews, so I just applied out of curiosity to see if I'd get the coupon for stickers. I did!
I guess it's a reasonably roundabout way to get a coupon for some stickers, if you need 'em.