Not surprisingly, I believe this is a common issue with companies whose HR departments are overloaded with applicants. I had a similar HR experience when applying to Riot Games. I'd passed the initial online assessment they use to presumably establish you are minimally educated, then received an email from the recruiter with a potential phone screen date. I promptly replied back, but didn't receive any confirmation until a couple days later, but only after I sent a follow up email. Also unusual were the times she was sending me emails - anywhere between 8pm to midnight.
The phone screen was equally unusual. She called me several minutes late, then gave forewarning that she would likely have to cut the phone screen short and complete the remainder at a later time because she needed to deal with another candidate who got lost coming into the office. Sure enough, she discontinued after about 10 minutes, and called back about 20 minutes later to finish the phone screen.
After the phone screen, she estimated that I would likely hear back from them by next week whether I would move to the next phone screen. I waited until the end week and sent a follow up email, and when she finally emailed me back, it had sounded like she completely forgot to pass my resume along altogether! She apologized for the delay and assured me she would get back to me soon after personally following up with the relevant hiring managers. Not surprisingly, I didn't hear back from her, so I waited a few more days and then gave her a call. I was as cordial and polite as could possibly be, but she didn't sound very happy to hear from me and promised she'd contact me soon, which never happened.
Needless to say, this was the most unusual hiring experience I've ever been through, and my initial enthusiasm has dampened significantly. I honestly would have preferred if the process ran smoothly and I was fairly certain I didn't get the job, but it has been confusing and frustrating at every step in the process.