Tl;dr Unprofessional, rude and perhaps even slightly unhinged. Be alert or just stay away. 4 interviews, an SAT-type test (quite old fashioned), was told I passed all stages and impressed them, then got ghosted. Couldn't follow up as there were no contact details for people with answers. 2 weeks later suddenly get a generic "we decided to move forward with another candidate" email. There are more details which I cannot share here. Overall a convoluted, old fashioned, badly communicated and misleading process, which included some screaming too. My rule of thumb is - if they treat you this way as a candidate, there's absolutely no reason they would treat you better as an employee. Beware!