In theory it could but generally doesn't. What if he spent 2 weeks at "B" before continuing on to "C"?

AFAIK it has never gone as far as the Chief Counsel's office but the the orphaned and rejected Part 61 FAQ may be the "best" thing the FAA has ever said about what constitutes a single cross country "flight:"

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The 'original point of departure' does not change with a new day or delay
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To a large degree, what constitutes a single cross country flight is in the eye of the beholder, at least to the point where it becomes ridiculous. During an online discussion of the question, one person once said that he considers all of his flying to be one long cross country. That's a bit extreme but my guess is that so long as there is some reasonable basis for treating a flight with breaks as a single flight for cross country purposes it won't be questioned.

How long a break before it might be questioned? Beats me.