__tiered_open() includes the following code to initialize the btree for a tiered table:

    WT_ERR(__wt_btree_open(session, tiered_cfg));
    WT_ERR(__wt_btree_switch_object(session, tiered->current_id));

The call to __wt_btree_switch_object() is not needed since __wt_btree_open() opens the btree with the current active object – i.e., using tiered->current_id, for the objectID.