I found the HR to be very unprofessional. The HR interview was smooth and easy with basic questions. However, the technical interview was scheduled around 2-3 times and eventually in the end, there was no interview. What I found unprofessional was -
1) Multiple rescheduling of interview
2) No intimation from HR as to why it was rescheduled. I had to call them back to ask why.
3) No call after the last rescheduled date. There was no interview at all. And again, no intimation as to why.
4) Despite requesting thrice, I was not sent a formal email about the job description, though it was explained over phone during the HR interview.
I believe a simple intimation email won't take much time.