It does not match the behavior or regular tar. It is also unneeded. Time to take it out.

Consider a directory named only ".", or "./". On untar, should it change the permissions of the current directory? That is probably never what the user would want. So that file simply should not exist.

For any other file it is redundant, since tar extracts "./a" identically to "a".

I had some conversations with people building docker containers with pkg_tar and pkg_deb. They never understood what the leading "./" was for in bazel's rules. Most containers us straight, relative file paths.