Sigray Engineer interview questions

Process is HR phone screen, followed by technical screen, followed by team interview with presentation and lab tour. Although started smoothly, after the last interview, I've heard nothing since late September. I've attempted to follow-up with both contacts at Sigray at least three times; all three emails were ignored. In short: this company ghosts. Given the ghosting, I can only assume I've been rejected and their policy is to ignore any and all communication with candidates after that point. Ghosting--particularly after a multi-hour, onsite interview, that requires the interviewee to prepare an hour long presentation--comes across as very unprofessional, in contrast to the rest of the review process, and turned what was otherwise a positive interview experience into a negative one. Had I been merely rejected and *informed as such* and/or was otherwise communicated with in the event of extenuating circumstances, I'd have rated this process as positive.