One thing to note is that the person that added the commits only started contributing around late 2022 and appears to have a Chinese name. Might be required by law to plant the backdoor.
This does make me wonder how much they made a deliberate effort to build an open source portfolio so they’d look more legitimate when time came to mount an attack. It seems expensive but it’s probably not really much at the scale of an intelligence agency.
What's the salary for a software engineer in urban China? 60-80k/yr USD? Two years of that salary is cheaper than a good single shoulder fired missile. Seems like a pretty cheap attack vector to me. A Javelin is a quarter million per pop and they can only hit one target.