An index on (tenant, status, created) is one ordered structure keyed on the concatenated tuple. It is not three indexes, and it is not symmetric in its columns.

The ordering is lexicographic. So the only contiguous key ranges the structure contains are the ones pinned by a leftmost prefix:

(tenant)                     ✓ contiguous
(tenant, status)             ✓ contiguous
(tenant, status, created)    ✓ contiguous
(status)                     ✗ not a prefix
(created)                    ✗ not a prefix
(status, created)            ✗ not a prefix

A predicate on status alone names no contiguous range at all — the matching entries are scattered across the whole index, once per tenant. There is nothing to seek to, so the planner falls back to a sequential scan of the table.