The important point here is that this was an extraditional appeal hearing, not a trial. You're right to point out that the burden on Assange's lawyers was not to totally refute the charges or even to mount the best possible defense of Assange.
But you're also mischaracterizing the testimony a little bit, since I don't believe it's the case that everything Assange's lawyers stipulated was directly drawn from the extradition request. "She may have been upset, but she clearly consented" (I've slightly paraphrased) is an argument defending Assange from a valid charge, not an argument that the charge is invalid.
The testimony in this hearing probably does presage the testimony that'll be given in Sweden.
'In other words, this is Assange's lawyer saying "even if all you say is true this is why we believe there is no case". And you conveniently ignored the part where he provided that explanation for your last paragraph.'
It is not only the prosecutions claims, but it is also not in any way Assange's side of the story. It is the prosecutions claims plus an attempt by the lawyers at creating a plausible narrative within the constraints already laid down by the prosecutions claims without altering any of the prosecutions alleged facts.
But you're also mischaracterizing the testimony a little bit, since I don't believe it's the case that everything Assange's lawyers stipulated was directly drawn from the extradition request. "She may have been upset, but she clearly consented" (I've slightly paraphrased) is an argument defending Assange from a valid charge, not an argument that the charge is invalid.
The testimony in this hearing probably does presage the testimony that'll be given in Sweden.