Both China and Russia oppose America, but that doesn't mean they are full allies:
China and Russia may both be challenging the U.S.-led international order and the United States (though in different ways and perhaps to different levels), but they are not the same, and they are not likely to always act in unison. Within their partnership, there are most certainly differences in trajectory—a rising power and a declining power are likely to have different intentions and policies towards the international order.
While both countries may be revisionist, the degree to which they are coordinating in this revisionism is uncertain. While Beijing and Moscow may both want to change aspects of the international order, it is not clear whether they have a shared, formulated vision of an alternative order.
The author also essentially writes that China has to worry that a declining Russia linked to China might drag China into war with America before China has risen enough to challenge America with a good chance of success. Which is an excellent point.
But in practice could Russia drag China into a war with America? I can't imagine China joining a war with America that Russia starts. And I think it is unlikely China would side with Russia even if America started a war. China would prefer that Russia and China take each other down a peg and leave China out of it. China really just needs the image of alliance with Russia to bolster Peking's diplomatic weight, coupled with the hope of such a war between America and Russia.
In the short term the Russians are being paranoid, aggressive a-holes. But in the long term both America and Russia have an interest in opposing Chinese aggression. And Russians should realize that at some level rising China has an interest in using their declining friend Russia as a sacrificial pawn to weaken America--with a side benefit of weakening Russia which controls a lot of former Chinese territory in the Far East.
We really should be trying to pry Russia away from China's grip.
Anyway, the author thinks that thinking of rising China compared to America in terms of the dyad-based Thucydides Trap which says a rising power will provoke the declining power to wage war because it wants to hold its status is complicated by a declining Russia aligned loosely with China. The US-China/Russia relationship really isn't a dyad. That's a good point.
But I also think that the Thucydides Trap even in a pure America-China analysis is reduced by the distance between America and China. I really don't worry that America will start a war with China to stop China's rise.
Now, a war might begin for other reasons (with keeping Xi in power against internal opposition high on my list--and Russia should worry more than America in that case), but America has enough distance from China and geographic advantage to reduce a need to strike as past hostile dyads in close proximity have shown. Russia and China are the states close enough to have dangerous friction.
And then the big wild card is whether China can pass America in power, and if they can will they hold the top spot?