My experience is based off of being a Yale interviewer, so I am extrapolating what I am aware of from the Yale process to Columbia. The Harvard litigation also sheds light on the Harvard process for the period covered by the litigants’ discovery.
Since we are in late February, I would guess all first reads have been completed and candidates are being sorted into those going to committee (or subcommittees) for further consideration to make the Ivy date deadline about a month away.
Don’t know if Columbia prescreens interviews (or admits to prescreening). For Yale, it is generally a function of applicants in a region being assigned to available interviewers. Very few interviewees that I have had were admitted (probably consistent with admit rate). We did have an EA admit in my region this year without an interview, but it was a Questbridge student.