Before I left Amazon I tried transferring to multiple teams after speaking with hiring managers. They all (IIRC 4 separate ones) wanted either a full on-site loop or at minimum two coding interviews).
I was an L5 with about 5-6 years of experience, 1.5 at that point at Amazon.
Hiring managers have a lot of latitude at Amazon, so there isn't a consistent standard. I don't want to share too much PII but I was in a similar situation. I was able to transfer teams after an informal chat with a few engineers on the team (discussing past projects, the new team's product vision, etc.). There was no whiteboarding involved.
The hiring managers are themselves managers of the team e.g. for a team of devs, a software development manager. In parent comment's case, the manager likely asked for opinions from the team after the chats before giving the final approval.
IME, the best managers are the ones who trust and enable their teams to make the right decisions. It would be a red flag if the manager was just giving out offers without allowing the team to provide their input.
I was an L5 with about 5-6 years of experience, 1.5 at that point at Amazon.