The main Git bare cloning done during do_fetch doesn't download a copy of the binaries that a repository using Git LFS will eventually want. The checkout operation occurring as part of the do_unpack task, then, does this lazily. This violates the expectation that all network access happening during do_fetch.
Patch proposed: https://lists.openembedded.org/g/bitbake-devel/message/11909
Fixed with http://git.openembedded.org/bitbake/commit/?id=0efac66043662e7a2027192f50e92e982db2ba1c