Google data center engineer interview experience

I got feedback from my Google recruiter that though my interview feedback has been very positive however they have selected another candidate for the L5 position. Before this update, the recruiter emailed me twice telling me that the feedback of my interviews have been very positive and they will update me soon. This naturally led me to a hopeful outcome. Recruiter told me four interviewers gave me excellent rating and one gave me good rating. They said my inclined loop is valid for 18 months and they will try to find another role or if another position for same role is opened.

In this process, I felt the hiring manager interview was little strange. After initial introduction and what the role is about, I was expecting they would like to know about me and ask some questions around technical leadership etc but they didn't ask me much. During my introduction, I explained in detail about my background and various industries i worked up until this point and opened the discussion quite a bit so if they have any follow up, we could have an engaging conversation. They asked me one other question and in response I gave them a good detailed answer and also asked if I answered what they were trying to get. His response was 'I agree with your analysis'. Other questions they asked were 'how did we find you like did recruiter reached out etc' and 'do you need immigration support (I don't btw, I've green card)' and 'what do you do when you are not working '. In the end, I asked HM do you have any other questions. He said no I'm good. The 45 minute interview ended 20 mins earlier. After this interview, recruiter reached out to me telling me that my final interview with HM didn't happen. I told them that it did happen and I talked to HM. They mentioned all the interviewers entered their feedback except the HM. So the recruiter setup a quick 20 min call with HM. When the HM joined the call, I reminded them about our interview and he was able to refresh his memory. HM asked me what did we talk about. I told them all things we discussed, I had taken written interview notes for all my interviews so I pulled those out and told them in detail about our conversation. HM was little impressed with that telling me I remember more details than him. After this second call with HM, i sent them an email with couple other topics that we discussed and my response on those.

Overall, i felt bad and little disappointed with this experience especially the negligence by HM around entering feedback and not knowing what did they ask during interview. Is that typical or there's something else going on or I'm just overthinking ?

Couple things I tend to think

1. HM had already made their mind on hiring someone else and mine was just a placeholder. HM might have taken my interview as a standby candidate so if something fell through, they could reach me.

2. I suspect the other four interviewers gave me excellent rating except the HM. Those four interviews took full 45 mins and had great engaging conversations going deep on topics and giving me opportunity to express myself.

About me: I've been working in aws for 6+ yrs (L6 Sr engineer) and have 15 plus years experience overall.