I can tell you why the S/H tech crew made their decision. The deal on offer did not include any CPI rises to the hourly rate which, long term, grossly affects remuneration and super. It was in effect a four year pay freeze
Also a key plank of AIPA stance is that the company gives undertakings that on expiry of the EBA, that current conditions will remain intact. The company refuses to do this, quoting the line, "We do not intend to cancel the award so there is no need to put that in writing." Akin to North Korea saying, "We don't intend to ever use nuclear weapons so there is no need for us to agree not to build them."
It should be noted that this was not the actual EBA vote, but an internal AIPA poll, laying out the facts as the negotiating team sees them and asking for the opinion of the members whether further negotiation is required.
75% of respondents did not see the deal as being acceptable.