Note: I'm posting this as answer rather than adding it to the
question for two reasons: (1) I came up with this theory after I
posted the question and after I read the other answers (2)
adding this to the question would significantly change the
nature of the question and it'd be unfair to those who already
answered After reading answers from Derek and Ross, I came up
with a theory on how 度 and 回 differ from each other. Even though
this theory came from my observation and lacked reference, the
more I think about it the more probable it becomes so it might
be the case that it is actually true. Looking at the kanji for
回, it's the same kanji that is used for 回る, 回数, 回転 etc, which
all imply a circular flow, a rotation, a repetition. This nuance
of repetition is what 回 has and 度 lacks. The notion of repeating
event brings about another nuance: intention (if you are causing
the event to happen) and expectation (if you are just observing
it). When an event is known to repeat, there is an expectation
that it will hap