What should we expect from ARPA-H?

That seemed like the objection is more, it's going to be a slave to the existing orthodoxy as far as what's important/promising, rather than the politians, and the former is even worse if you're expecting novel thought or research directions.  Not sure to what extent that's actually true but reporting structure does matter; especially the topmost layer that still has strong technical opinions.

(I remark that the alternative mentioned in the Science article isn't "part of the OSTP" but "a standalone part of DHHS".)

Part of OSTP would be the good but it requires a political fight against the whole HHS. The people intereviewed chose the fight against the NIH because that's the easier fight to win but they still lost.

I'm not sure to what extent there's such a thing as the purpose for which DARPA was founded, but it seems to me you could equally say that cancer, diabetes and Alzheimer's aren't the purpose for which ARPA-H is being founded (assuming it actually happens)

I think the present scenario is that Biden's son died to brain cancer and Biden said on the campaign trial: “I promise you if I’m elected president, you’re going to see the single most important thing that changes America,” he said. “We’re gonna cure cancer.”

Given that the rest of the NIH funding increase is relatively small this does look like his strategy for curing cancer.

This is not the first time Biden tries to cure cancer. Biden personally wants cancer solved and is likely to push in that direction. At the same time between head of ARPA-H, head of NIH, head of HHS and the president that's a lot of maze levels and that's only the top of of the organization and you can expect at least two additional maze level till it goes to the individual who heads the team that gets a grant and an additional at least one additional maze level for the people who work on the grant. 

The article in Science quotes some people who think ARPA-H will probably do well and some who don't.

Of course it does. Why wouldn't it? Why would it tell us anything that Science tries to present both sides? 

One the one hand you have biomedical scientists speaking about problems with ARPA-H and on the other hand you have an organization headed by a chair with a BA in English who describes herself as a thought leader with is a general tell for someone who engages in bullshit and a CEO who describes her background as "political science, sociology, and the humanities". 

If the Biden administration wants something that will be able to engage in grand and innovative projects in the realm of health but has wrong ideas about how to get that

That sort of depends who you count as the Biden administration. Biden himself wants grand and innovative projects in the realm of health. On the other hand you have the NIH and surrouding players wanting more NIH funding and enough political power to get Biden to chose the structure he chose. When I say "pretends" I'm counting the people with the power to set the structure inside the Biden administration.

by politically-charged emotions, whether positive ("ha, nice to see someone seeing the Biden administration for the bullshitters they are") or negative ("why is this guy posting a political attack piece on LW under the guise of a question?"). 

There are two levels here. One level is caring about US party politics and the other is caring about the infrastructure of intellectual progress and the disfunction of what happens inside the HHS. I find the second much more important. Zvi writes nearly every week strongly worded content that attacks what happens inside the HHS. Being opinionated about the HHS is part of normal LW discourse. 

In this particular instance Biden plays more of a role then for the usual HHS issues but just because Biden touches the issue more, I don't think that's a reason to use less opinionated wording. 

Anyone getting mind-killed by the party politics is not going to be able to think well about the issue of what happens inside the HHS no matter how I word the question.