It is entirely unreasonable to assume that there is any statistically significant proportion of those plugin crashes that aren't Flash (well, maybe a few Java crashes...). Apple can't publicly blame Flash with any specificity, because they can't have Flash for OS X get abandoned until their mobile strategy has mostly killed Flash anyways. But they still have the raw data and stack traces. And that data indicates that Flash is by far the most crash-prone app on most Macs.