The greater concern should be how many other sleeper contributors are out there. Anonymous contributions are accepted every day, and we know of cases with malicious intent such by "James Bond" (https://lore.kernel.org/lkml/20200809221453.10235-1-jameslou...).

I am not specifically worried about other contributions by "Jia Tan", those are being extensively looked at right now. They and other sleepers may just as well have contributed to any project with a different name and therefore "Jia Tan" does not pose more danger than any other contribution whose submitter cannot be held responsible.