It's hard to see this account (jbang5) as anything but an internet troll who, if not literally on the payroll from the Chinese government, is still a useful idiot for their cause.
What I usually do, to counter this trolling tactic, is to provide them with the source that they were asking for, and then I call them an idiot for not being aware of such an obvious fact.
Because, by definition, they are uninformed about the matter, as they didn't know about the source and had to ask for it. So I just make fun of them for not knowing about it, and rub it in their face when I provide the information that they asked for and didn't know about.
If you have to ask for sources on the matter, you are by definition "ignorant" on the matter.
Based off of this web comic: http://wondermark.com/c/2014-09-19-1062sea.png
https://lmgtfy.com/?q=china+icloud+encryption+keys
You could also look at some of the other links already posted to this thread in response to similar queries from you and others, like this one (https://news.ycombinator.com/item?id=21207931) and this one (https://news.ycombinator.com/item?id=21208376).
Tianhe-2 Supercomputer @ 33.86 petaflops (quadrillion flops)
=33 860 000 000 000 000 keys per second (33.86 quadrilion)
3.386e16 * 31556952 seconds in a year 2255 possible keys
2^255 / 1.0685184e24
=1.0685184e24 keys per year (~1 septillion, 1 yottaflop)
=5.4183479e52 years
Needless to say, that's a long fucking time. Yes, cracking an access password would be much less time-consuming and so would finding and using non-brute force attack methods to guess or steal the key but for your basic claim that "Yes", China has cracked strong encryption, I just don't see where you get that idea from.