S5 Stratos interview questions

I went through 5 rounds of interviews with the company, including a practical assessment and a 2 hour interview with the CEO on a Saturday. I was verbally offered a job and we agreed upon a salary. We discussed some follow-ups regarding AI research but it was stressed there was no timeline and the team would be in touch soon to finalize the offer. I had to follow up twice over three weeks to receive a response from the company. The response was had I sent the CEO the follow ups we discussed. I had not because of our conversation and I was not going to continue to do work without a formal offer. I rescinded my candidacy following this response. Throughout the process I received emails over the weekend and overnight which is unprofessional.