(1) I included the uncertainty brought by the 3-items-buffer in the calculations. Technically, I COULD have eliminated the uncertainty by checking the splitters with the dismantle tool right at the end of each test, but for practical reason I didn't (I'd rather just add more buffers to make the test more precise)
(2) That test was made (iirc) either on a single segment or a 2 segments long belt. I think running the same test for 1h on a 20+ segments belt would be indicative of wether the issue could be detectable by the general efficient user or not (by this I mean: if the issue causes at least 1 reduction in efficiency every hour, people monitoring the power draw or yellow lights would notice).
(4) It's fine if item buildups on belt disappear, but if they do go on different paths due to smart splitters before one restarts the game there will be effects on the machines (eg: Uranium line at 780/min into a factory with connection to sink for overflow).
(5) The semantics of wether the "bug" has been fixed or not don't quite interest me, I'll take your word on that. But practically speaking, there are still the same considerations to be done as in U6 when dealing with maxed belts when one wants perfection. As I said, this is not something I mention often anyway and always accompany with knowledge on wether this can affect their gameplay or not (which allows one to decide wether they care or not).
I'd rather end up spending 5 extra minutes reassuring someone they won't have to worry about the issue, then hours trying to make sure wether that one big builder who wants max efficiency is actually suffering of throughput losses or just any other sort of user error somewhere