If you have a revision graph like:
a----B----c----D----e
\
\--f----g
where you only change a file (e.g. .hgtags) in revisions "B" and "D",
even though "g" is a head of the repo, it doesn't point to a head of the
filelog.
I don't think storing deletion records in the filelog would help this
case.
Alexis