A point about this bit at the very end,
The new death-house provides for the liquidation of 8,000 to 10,000 victims. If we consider that right now 2,000,000 murdered Jews, or the greater part of Polish Jewry, are already buried in the area of Treblinka, the disturbing question arises: for whom do the S.S. intend that new house of death; who are to utter their last breath in the slaughter-house? Most probably the death machine, once started, will not limit itself to murdering Jews. At present, the specter of death in steam chambers rises before the Polish population; there have already been some signs of it: according to a report of an eyewitness, the Germans exterminated a group of Poles in death house No.1, in the second half of August.
If the smaller "death house" had been sufficient to kill 2,000,000 people, it is hard to see the logic in building a
larger "death house." The propagandists suggest that this larger death house was being built in order to steam, ahem, gas
Gentile Poles, presumably many millions of them. As this was sent to London, I would bet the intention here was to rile up the Poles.
For a bit of context on these two gas chamber buildings,
Arad (Ch 17) says, "Construction on the new gas chambers began in
early September." Later he says, "With the inauguration of the new gas chambers, in
the middle of October 1942, the old ones ceased to function."
Wiernik claims he helped build the second gas chamber building, and says it took five weeks: "The work on these gas-chambers lasted five weeks, which, to us, seemed like centuries. We had to work from dawn to dusk under the ceaseless threat of beatings with whips and rifle butts."
The modern version of the story of course rejects this 2,000,000 number. But the numbers still don't fit that well with the timeline of the gas chamber construction.
Here are some rough numbers (from Dalton's death matrix)
Jul: 175K
Aug: 135K
Sep: 165K
Oct: 185K
Nov: 100K
Dec: 40K
Total 1942: 800K
And he has another 100K for all of 1943 without any monthly split.
By mid-October, most of the killing would have been done with, so there would not have been much point in building this second gassing building. Unless you were planning on gassing a bunch of Gentile Poles which is not longer claimed.