git vs hg commit counts?

I'm comparing linux-kernel git vs hg repositories.

While testing some changes to scripts/get_maintainer.pl, I noticed that git and hg have different commit counts for the same files.

For instance:

$ git log --since=1-year-ago -- MAINTAINERS | \
	grep -P "^commit [0-9a-f]{40,40}$"  | wc -l
514

$ hg log --template="commit {node}\n" --date -365 -- MAINTAINERS  | \
	grep -P "^commit [0-9a-f]{40,40}$" | wc -l
601

Anyone have any understanding why?