I don't think it's about growing fast so much as, from those I talked to, Amazon now has a fairly bad reputation in the tech community. You only go to work there if you don't have a better option (Google, Facebook, etc) or have some specialty skill they're willing to pay for. Pay is below other FAANG companies and the work culture isn't great (toxic even some would say).
edit: They also had the most disorganized and de-centralized interview approach from all the FAANG companies I talked with. Which isn't growing pains this far in, it's just bad management and process.
I interviewed as a new grad SWE and the process was totally straightforward, and way lower friction (albeit much less human interaction, which made it feel even more impersonal) than almost everywhere else I applied: initial online screen, online programming task, and then a video call with an engineer where you explained your answer to the programming task.
I was doing machine learning so more specialized than regular SDE. Other companies it was talk to recruiter, phone screen with manager, and then virtual onsite interviews. Hiring was either not team specific or the recruiter helped manage the process (ie: what does this role actually need). Very clear directions on what type of questions will be asked, format of the interviews, what to prepare for, etc. Amazon the recruiter just told me to look on the job site and then, despite me being clear, applied me to the wrong role. Then got one of those automated coding exercises despite 15 year experience and an internal referral. Wasn't hard but it also pointless since the coding exercise was for the wrong role. Finally got a phone screen and they asked me nothing but pedantic college textbook questions for 40 minutes. Recruiter provided no warning for that.
edit: You could blame the recruiter but every other company had a well oiled machine for their recruiters. So even if they provided only generic information there was still a standard process for what they provided.
SWEs who weren't just recently promoted to L5 at Amazon. They have some experience at that level. Granted, there could be some bias because it's not easy to pinpoint when they were promoted.
edit: They also had the most disorganized and de-centralized interview approach from all the FAANG companies I talked with. Which isn't growing pains this far in, it's just bad management and process.