It's a difficult one. Personally I don't think we would have sold 3k, over 2k definitely without doubt, say 2350 for arguments sake. It's that upper and lower tier thing with the catering facilities, you just can't slide a line of stewards left or right to take up the slack or at least that's clearly what Villa are saying.
My guess is Villa also need to know if they can shift 1500 tickets or not so perhaps they set the timescale, more stewarding / policing for away fans probably needs organising as well.
The original communication from the club was slightly disingenuous however. As you said earlier it was always going to be the lower tier, it didn't need to meet any criteria as the club suggested, as none of us have a clue what criteria they use anyway.