Eddy, I'm not sure the specific clause "Dont announce strike dates" would have been added, more that the offer was conditional upon no industrial action, which due to the costs involved would have invalidated the offer.
I believe somebody in BASSA/Unite thought they could be clever with whether announcing dates counted as industrial action, missing the point of costs mounting as soon as dates were announced.
Lets also be clear, time was not running out, as Derek Simpson and WW had agreed to extend the ballot mandate by 28 days, to give Unite time to poll its members.
BASSA wanted to have its cake (strike dates) and eat it(original offer) without realising the two were mutually exclusive.