'I would indeed say that both the man himself, and his crossing of the Rubicon, are things which no longer exist in any sense at all.'

This does sound like presentism. If we understand you. It is indeed a radical view, exceedingly controversial and widely rejected, though
it is certainly widespread outside of philosophy and physics--the 'ordinary person's' view ('the past is no more, the future is yet
to be, only the present is real').   Multiple objections to it, in fact. There are some presentists left, but nobody is in a position to help themselves to it as a premise
in an argument.