I think the key point in the memo is "The following assumptions were made for purposes of calculating the potential value of GS7340 as an exclusivity extension

I think the key point in the memo is "The following assumptions were made for purposes of calculating the potential value of GS7340 as an exclusivity extension strategy: GS7340 exhibits incrementally better efficacy (greater antiviral log reduction when taken as a monotherapy) than Viread. At the time the decision was made, nobody knew if the drug would be better. There were two possible outcomes if they made the investment now: a) the drug turns out to be a flop, the investment is lost or b) the drug turns out to be better. And the decision was not "do we continue to develop this now", it was "do we develop this now, or spend the R&D dollars on something else". It is true that the patent expiration was a factor, but the fact the drug turned out to be better is just 20/20 hindsight. If it had failed and Gilead flushed a few hundred million down the drain, nobody would have criticized the decision to delay the development.