Actually PerplexShyt, it does matter that the phone was idle. He didn't have to go into usage screen to check on cellular usage because he jailbroke his phone and took a data dump of what happened during that idle time. And within that idle time, the poster noticed a constant 1 k/s stream. He bypassed the usage screen through jailbreak.
But again your point about the usage screen is not what we're getting at here. Browsing the usage screen and retrieving quota should be a small operation size wise. If you look at the "debunk" thread you guys reference, checking usage amounts to a 1-2 kb increase (per Jimbo47's findings). In order to achieve a 1 k/s increase for 2 hours, the user would have to click back and forth through the usage pages about once every second to 2 seconds for 2 hours. Why would the hackernews poster be testing it that way?
Again, yes when you browse the usage screens your cellular data will increase - we are not debating this. It is the scale at which the increase happens from whatever bug/situation is happening that implies that this has nothing to do with usage checking.
I would also like to point out what while battery draining is definitely an inconvenience, this excessive cellular data bug/issue actually does much more damage as it drives up 3g use. For those within a data quota, they could be billed a huge amount.