Earlier quoted context omitted.
There is a lot of middle ground between keeping something secret until there's something take-it-or-leave-it vs. publishing every "what if we do X, will you then let us do Y" back and forth. If more intermediate work products are unfit for public eyes, perhaps they shouldn't be going there in the first place.
OK but what would they publish? General ideas? The details being published would only lead to a mess as each company could advertise and make a fuss over things. Or other countries might do the same to shift things in their favor. The end goal for each country is to do things to benefit themselves, even if it means making hard decisions. It's not like spy exchange negotiations or all other sorts of diplomatic process…
Whether or not "publishing each move" is beneficial depends on what "each move" is. I agree that at the most fine grained level, you don't want everyone to find out how far you were willing to go in conversations with one opposing negotiator, in case you need to negotiate similar clauses with someone else, for example.
But once you have agreed that you're giving X in return for Y, publishing that should not do much harm unless giving X is controversial. In which case the "harm" might be exactly what ought to happen.
Here's another example, which is more relevant:
During Norways EEA negotiations with the EU, the Norwegian press reported details pretty much daily. I just checked the archive of one of Norways largest papers to confirm my memory, and from '90 to '92, EEA was mentioned about 5000 times, and included things like government ministers informing the press about likely contents of Norwegian negotiation positions that had not yet been presented to the EU (but where the overall lines of the EU position was known - in one case I looked at, the minister confirmed that the Norwegian position would overall come close to what the EU had asked for in terms of regulation of granting operating licenses for EU companies in certain areas).
They certainly did not get access to everything, but they got regular briefings, and it contributed to ensuring the debate over whether or not to join the EEA shaped the negotiations, as the sitting, pro-EEA government got very clear signals about which concessions would cause the biggest problems with the opposition and/or cost them voters.