If you look up ‘beyul khenpajong’ on yandex or duckduckgo, you get almost exclusively articles about Chinese aggression and some tourism stuff. Most of them came out between March and August 2021, and the original source in English appears to be a Foreign Policy article from February 2021. That same article is what they are following up on, here. They also all use some variation of a phrase about the valley (which is what ‘beyul’ means) being sacred to Buddhism or important to the royal family of Bhutan. The smug phrasing about how awful and aggressive China is sets my teeth on edge.

Reading between the lines of this article, China and Bhutan have had a number of territorial disputes since the 80s, running down from the PRC liberating Tibet. In the FP article, they even quote a Tibetan exile slaver who refuses to comment on whether Tibet has a right to the lands in question even though he says China does not. The point of these articles is to create a unfalsifiable sense of truth. If there are ten articles, all saying more or less the same thing, from different sources, across months or years, then they must be on to something. It hardly matters if it’s the same three claims from the same source, repackaged over and over.

It looks like China is building up in two valleys or villages in the hopes of switching them for the ones they actually want. i do not know what areas, specifically, they want or why they want them. Taking over an important valley and giving it infrastructure improvements in hopes of a swap seems to reflect a rational negotiating strategy. Any and all mention of fortifying the border with India or provoking India is journalistic malpractice if they do not mention that this is the border where members of the Chinese and Indian army cannot have guns, and beat each other with pole arms. This region is rough terrain, to put it mildly, so there is no risk of an army from either side sneaking in via a handful of extra runways and helicopter pads. If China was actually the devil, they would take the land they wanted by force of arms or they would offer some BRI project or debt relief plan that Bhutan couldn’t refuse

Oops I didn't see you reposted here so I'll post my response here as well.

I can think of a a few reasons they would do this. Bhutan is an Indian vassal (although less so now than in the past) so this could put pressure on India to resolve their (China's and India's) border dispute. India has repeatedly refused very advantageous (for India) solutions like the Package Deal, proposed by China multiple times since 1960, where China gets Aksai Chin (with a civilian population of 0 and an area of 38,000 km²) and India gets Arunachal Pradesh (with a population of 1.4 million and an area of 83,743 km²).

Another reason could be to pressure Bhutan directly for a number of reasons. It could be to get Bhutan to recognize China as a country, which it hasn't done since the founding of the PRC (it doesn't recognize the RoC either). It could be to get Bhutan to stop dragging it's feet (in general it seems that feet-dragging is the default mode of operation of the Bhutanese government) with actually settling the border, which it has also never done. It could also be to get Bhutan to officially give up their claims on their former enclaves inside China, of which there are many, mostly in Tibet but iirc there are a few in other provinces (India also has at least one that it hasn't given up claims on).

I wrote most of this from memory and I'm not super well read on the topic so there are probably some inaccuracies.