Does GNU tar incremental backup save an entire file again, even if only atime or mtime is different?

mkdir test
echo "hi" > test/file1
tar -c -f archive.0.tar -g test.snar test
touch -a test/file1  # changes atime and ctime, doesn't change mtime
tar -c -f archive.1.tar -g test.snar test
tar -t -G -vv -f archive.1.tar  # lists Y for file1

So did GNU tar store the entire file again, even though only access time (atime) and metadata change time (ctime) were changed? This seems horribly inefficient to me, as we can reasonably expect many files to be read but not changed.